Port all development-branch features into kBenestad redesign

- Bidirectional FX rate entry: rcur dropdown (e.g. "35 THB per USD" or
  "0.028 USD per THB") with rother label updating dynamically
- FX labels from config translations; currency code appended at runtime
- ct-pick persisted to localStorage; restoreStorage rebuilds client-
  specific project code options before re-applying saved pcode value
- Footer rebuilt by buildFooter() with dynamic About link
- About modal with markdown-rendered content from config.yml (marked.js)
- about section added to config.yml with EN/DE/FR/NO content
- rcur saved/restored in inv_lines_v1; gatherData includes rcur in fxNote
- relabel() calls updateFxLabels() for each active FX line on lang switch

https://claude.ai/code/session_01MkM7p8Us3L8YAfLKGA13NS

app/config.yml

@@ -21,6 +21,58 @@ languages:
     name: Norsk
     direction: ltr
 
+# ── About modal ───────────────────────────────────────────────────────────────
+# Optional. Remove this section entirely to hide the About link in the footer.
+about:
+  en:
+    title: "About"
+    content: |
+      ### Invoice Generator
+      A single-file browser app for generating freelance invoices as PDF.
+      No backend, no build step — just a browser and a config file.
+
+      **Source:** [kbenestad/invoice](https://github.com/kbenestad/invoice)
+      **Docs:** [docs.benestad.net/invoice](https://docs.benestad.net/invoice)
+
+      © 2026 Kristian Benestad. Licensed under the Apache 2 license.
+    btn-close: "Close"
+  de:
+    title: "Über"
+    content: |
+      ### Rechnungsgenerator
+      Eine Single-File-Browser-App zur Erstellung von Freiberufler-Rechnungen als PDF.
+      Kein Backend, kein Build-Schritt.
+
+      **Quellcode:** [kbenestad/invoice](https://github.com/kbenestad/invoice)
+      **Dokumentation:** [docs.benestad.net/invoice](https://docs.benestad.net/invoice)
+
+      © 2026 Kristian Benestad. Lizenziert unter Apache 2.
+    btn-close: "Schließen"
+  fr:
+    title: "À propos"
+    content: |
+      ### Générateur de factures
+      Une application de navigateur en fichier unique pour générer des factures en PDF.
+      Aucun backend, aucune étape de build.
+
+      **Code source :** [kbenestad/invoice](https://github.com/kbenestad/invoice)
+      **Documentation :** [docs.benestad.net/invoice](https://docs.benestad.net/invoice)
+
+      © 2026 Kristian Benestad. Sous licence Apache 2.
+    btn-close: "Fermer"
+  "no":
+    title: "Om"
+    content: |
+      ### Fakturagenerator
+      En nettleserapp i én fil for å generere frilansfakturaer som PDF.
+      Ingen backend, ingen byggtrinn.
+
+      **Kildekode:** [kbenestad/invoice](https://github.com/kbenestad/invoice)
+      **Dokumentasjon:** [docs.benestad.net/invoice](https://docs.benestad.net/invoice)
+
+      © 2026 Kristian Benestad. Lisensiert under Apache 2.
+    btn-close: "Lukk"
+
 # ── Payment info visibility ───────────────────────────────────────────────────
 # Set to true to hide the payment info panel entirely (useful if payment info
 # should not appear on invoices, e.g. per company policy).
@@ -355,25 +407,25 @@ translations:
     fr: Devise étrangère
     "no": Utenlandsk valuta
   currency-code:
-    en: Currency code
-    de: Währungscode
-    fr: Code devise
-    "no": Valutakode
+    en: Foreign currency code
+    de: Fremdwährungscode
+    fr: Code devise étrangère
+    "no": Utenlandsk valutakode
   exchange-rate:
-    en: "Exchange rate (X foreign = 1 local)"
-    de: "Wechselkurs (X Fremd = 1 Inland)"
-    fr: "Taux de change (X étranger = 1 local)"
-    "no": "Valutakurs (X utenlandsk = 1 lokal)"
+    en: Exchange rate
+    de: Wechselkurs
+    fr: Taux de change
+    "no": Valutakurs
   per-item:
-    en: Price per item (foreign currency)
-    de: Preis je Einheit (Fremdwährung)
-    fr: Prix par unité (devise étrangère)
-    "no": Pris per enhet (utenlandsk valuta)
+    en: Price per item in
+    de: Preis je Einheit in
+    fr: Prix par unité en
+    "no": Pris per enhet i
   total-foreign:
-    en: Line total in foreign currency
-    de: Zeilenbetrag (Fremdwährung)
-    fr: Total ligne en devise étrangère
-    "no": Linjebeløp i utenlandsk valuta
+    en: Line total in
+    de: Zeilenbetrag in
+    fr: Total ligne en
+    "no": Linjebeløp i
   add-line:
     en: "+ Add new line"
     de: "+ Neue Zeile hinzufügen"

app/index.html

@@ -400,11 +400,21 @@
 
 </div><!-- /.kb-wrap -->
 
-<footer class="kb-footer">
-  <span>&#169; 2026 kBenestad</span>
-  <span class="sep">&#183;</span>
-  <a href="https://github.com/kbenestad/invoice">kbenestad/invoice</a>
-</footer>
+<!-- About modal -->
+<div id="about-modal" style="display:none;position:fixed;inset:0;z-index:999;
+     background:rgba(0,0,0,.45);align-items:center;justify-content:center;padding:20px">
+  <div style="background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);
+              box-shadow:var(--shadow);max-width:520px;width:100%;padding:28px 28px 20px">
+    <h2 id="about-dialog-header" style="font-size:18px;font-weight:700;margin:0 0 16px;color:var(--text)"></h2>
+    <div id="about-dialog-body" style="font-size:var(--fs-base);color:var(--text-soft);line-height:1.65;
+         max-height:60vh;overflow-y:auto"></div>
+    <div style="margin-top:20px;text-align:right">
+      <button id="about-btn-close" class="kb-btn kb-btn--ghost" onclick="closeAbout()">Close</button>
+    </div>
+  </div>
+</div>
+
+<footer id="app-footer" class="kb-footer"></footer>
 
 <!-- js-yaml -->
 <script src="https://cdnjs.cloudflare.com/ajax/libs/js-yaml/4.1.0/js-yaml.min.js"
@@ -412,6 +422,9 @@
 <!-- jsPDF -->
 <script src="https://cdnjs.cloudflare.com/ajax/libs/jspdf/2.5.1/jspdf.umd.min.js"
         crossorigin="anonymous"></script>
+<!-- marked (About modal markdown) -->
+<script src="https://cdn.jsdelivr.net/npm/marked/marked.min.js"
+        crossorigin="anonymous"></script>
 
 <script>
 "use strict";
@@ -583,6 +596,7 @@ async function loadCfg() {
 function boot() {
   buildLangBar();
   buildForm();
+  buildFooter();
   restoreStorage();
   if (!loadLines()) addLine();
   document.getElementById("loading").style.display = "none";
@@ -614,8 +628,7 @@ function buildLangBar() {
   const langs = cfg.languages || [{ code: cfg["default-code"], name: cfg["default-name"] }];
   if (langs.length < 2) return;
   const part = document.getElementById("lang-part");
-  if (part) part.style.display = "flex";
-  document.getElementById("lbl-language").textContent = t("language");
+  if (part) part.style.display = "";
   const sel = document.getElementById("lang-sel");
   sel.innerHTML = langs.map(l =>
     `<option value="${h(l.code)}" ${l.code === lang ? "selected" : ""}>${h(l.name)}</option>`
@@ -768,7 +781,7 @@ function buildForm() {
   <section class="kb-card">
     <h2 class="kb-card__title">
       <span id="sec-ct">${t("charge-to")}</span>
-      <select id="ct-pick" class="kb-select"
+      <select id="ct-pick" class="kb-select" data-ls="ct-pick"
               style="width:auto;font-size:var(--fs-small);margin-left:8px;padding:4px 28px 4px 8px">
         <option value="">${t("select")}</option>
         ${ctOpts}
@@ -1138,24 +1151,33 @@ function toggleFx(i) {
   fxDiv.innerHTML = `
     <div class="kb-grid cols-3">
       <div class="kb-field">
-        <span class="kb-label">${t("currency-code")}</span>
+        <span class="kb-label" id="fcur-lbl-${i}">${t("currency-code")}</span>
         <select id="fcur-${i}" class="kb-select"
                 onchange="updateFxLabels(${i});calcLine(${i});saveLines()">
           ${currOpts(defaultFcy)}
         </select>
       </div>
       <div class="kb-field">
-        <span class="kb-label" id="frate-lbl-${i}">Exchange rate (X ${h(defaultFcy)} = 1 ${h(lcy)})</span>
-        <input type="number" id="frate-${i}" class="kb-input num" value="" min="0" step="any"
-               oninput="calcFxFromPer(${i})">
+        <span class="kb-label" id="frate-lbl-${i}">${t("exchange-rate")}</span>
+        <div style="display:flex;align-items:center;gap:6px;flex-wrap:wrap">
+          <input type="number" id="frate-${i}" class="kb-input num" value="" min="0" step="any"
+                 style="flex:1;min-width:70px" oninput="calcFxFromPer(${i})">
+          <select id="rcur-${i}" class="kb-select" style="width:auto"
+                  onchange="updateFxLabels(${i});calcFxFromPer(${i});saveLines()">
+            <option value="${h(lcy)}">${h(lcy)}</option>
+            <option value="${h(defaultFcy)}">${h(defaultFcy)}</option>
+          </select>
+          <span class="kb-label" style="margin:0">per</span>
+          <span id="rother-${i}" style="font-size:var(--fs-small);font-weight:600;color:var(--text)">${h(defaultFcy)}</span>
+        </div>
       </div>
       <div class="kb-field">
-        <span class="kb-label" id="fper-lbl-${i}">Price per item in ${h(defaultFcy)}</span>
+        <span class="kb-label" id="fper-lbl-${i}">${t("per-item")} ${h(defaultFcy)}</span>
         <input type="number" id="fper-${i}" class="kb-input num" value="" min="0" step="any"
                oninput="calcFxFromPer(${i})">
       </div>
     </div>
-    <div class="fx-note">${t("total-foreign")}: <strong id="fltot-${i}">0.00</strong></div>`;
+    <div class="fx-note"><span id="ftot-lbl-${i}">${t("total-foreign")} ${h(defaultFcy)}</span>: <strong id="fltot-${i}">0.00</strong></div>`;
   lr?.insertAdjacentElement("afterend", fxDiv);
   calcLine(i);
   saveLines();
@@ -1164,8 +1186,12 @@ function toggleFx(i) {
 function calcFxFromPer(i) {
   const per  = pn(document.getElementById(`fper-${i}`)?.value);
   const rate = pn(document.getElementById(`frate-${i}`)?.value) || 1;
+  const rcur = document.getElementById(`rcur-${i}`)?.value;
+  const lcy  = document.getElementById("icur")?.value || "";
   const prEl = document.getElementById(`price-${i}`);
-  if (prEl) prEl.value = (per / rate).toFixed(6);
+  if (prEl) prEl.value = rcur === lcy
+    ? (per * rate).toFixed(6)
+    : (per / rate).toFixed(6);
   calcLine(i);
   saveLines();
 }
@@ -1247,6 +1273,17 @@ function restoreStorage() {
       if (el) el.value = v;
     });
 
+    // Restore charge-to: rebuild its project code options then re-apply pcode.
+    // fillChargeTo() calls updateProjectCodes() which resets the pcode select,
+    // and may call saveStorage() mid-flow, so we re-apply and re-save after.
+    const ctPickEl = document.getElementById("ct-pick");
+    if (ctPickEl?.value) {
+      fillChargeTo(ctPickEl.value);
+      const pcodeEl = document.getElementById("pcode");
+      if (pcodeEl && d.pcode) pcodeEl.value = d.pcode;
+      saveStorage();
+    }
+
     if (d.pcode === "__other__") {
       const w = document.getElementById("pcode-other-wrap");
       if (w) w.style.display = "block";
@@ -1310,6 +1347,7 @@ function relabel() {
       fe.innerHTML = `<option value="no">${t("no-option")}</option><option value="yes">${t("yes")}</option>`;
       fe.value = s;
     }
+    if (document.getElementById(`rcur-${i}`)) updateFxLabels(+i);
   });
 
   const alBtn = document.getElementById("btn-al");
@@ -1410,10 +1448,11 @@ function gatherData(renderLang) {
     let fxNote = null;
     if (isFx) {
       const cur        = document.getElementById(`fcur-${i}`)?.value || "";
+      const rcur       = document.getElementById(`rcur-${i}`)?.value || "";
       const rate       = pn(document.getElementById(`frate-${i}`)?.value) || 1;
       const per        = pn(document.getElementById(`fper-${i}`)?.value);
       const foreignTot = per * qty;
-      fxNote = { cur, rate, per, foreignTot, td };
+      fxNote = { cur, rcur, rate, per, foreignTot, td };
     }
     rows.push({ qty, uomLbl, desc, price, tot, fxNote });
   });
@@ -1652,12 +1691,24 @@ function buildPDF() {
 
 // ── Update FX labels when currency or invoice currency changes ────────────────
 function updateFxLabels(i) {
-  const fcy = document.getElementById(`fcur-${i}`)?.value || "FCY";
-  const lcy = document.getElementById("icur")?.value || "";
+  const fcy      = document.getElementById(`fcur-${i}`)?.value || "FCY";
+  const lcy      = document.getElementById("icur")?.value || "";
+  const rcurEl   = document.getElementById(`rcur-${i}`);
+  const rotherEl = document.getElementById(`rother-${i}`);
+  if (rcurEl) {
+    const prev = rcurEl.value;
+    rcurEl.innerHTML = `<option value="${h(lcy)}">${h(lcy)}</option><option value="${h(fcy)}">${h(fcy)}</option>`;
+    rcurEl.value = (prev === lcy || prev === fcy) ? prev : lcy;
+  }
+  if (rotherEl) rotherEl.textContent = rcurEl?.value === lcy ? fcy : lcy;
+  const cl = document.getElementById(`fcur-lbl-${i}`);
+  if (cl) cl.textContent = t("currency-code");
   const rl = document.getElementById(`frate-lbl-${i}`);
+  if (rl) rl.textContent = t("exchange-rate");
   const pl = document.getElementById(`fper-lbl-${i}`);
-  if (rl) rl.textContent = `Exchange rate (X ${fcy} = 1 ${lcy})`;
-  if (pl) pl.textContent = `Price per item in ${fcy}`;
+  if (pl) pl.textContent = t("per-item") + " " + fcy;
+  const tl = document.getElementById(`ftot-lbl-${i}`);
+  if (tl) tl.textContent = t("total-foreign") + " " + fcy;
 }
 
 // ── Save / load invoice lines ──────────────────────────────────────────────────
@@ -1676,6 +1727,7 @@ function saveLines() {
       price: document.getElementById(`price-${i}`)?.value || "",
       fx:    document.getElementById(`fx-${i}`)?.value    || "no",
       fcur:  document.getElementById(`fcur-${i}`)?.value  || "",
+      rcur:  document.getElementById(`rcur-${i}`)?.value  || "",
       frate: document.getElementById(`frate-${i}`)?.value || "",
       fper:  document.getElementById(`fper-${i}`)?.value  || "",
     });
@@ -1725,6 +1777,10 @@ function loadLines() {
             const el = document.getElementById(`fcur-${i}`);
             if (el) { el.value = ld.fcur; updateFxLabels(i); }
           }
+          if (ld.rcur) {
+            const el = document.getElementById(`rcur-${i}`);
+            if (el) { el.value = ld.rcur; updateFxLabels(i); }
+          }
           if (ld.frate) { const el = document.getElementById(`frate-${i}`); if (el) el.value = ld.frate; }
           if (ld.fper)  { const el = document.getElementById(`fper-${i}`);  if (el) el.value = ld.fper; }
           calcFxFromPer(i);
@@ -1757,6 +1813,48 @@ function resetLines() {
   calcTotals();
 }
 
+// ── Footer & About modal ──────────────────────────────────────────────────────
+function aboutData() {
+  const ab = cfg?.about;
+  if (!ab) return null;
+  return ab[lang] ?? ab[cfg["default-code"]] ?? Object.values(ab)[0] ?? null;
+}
+
+function buildFooter() {
+  const footer = document.getElementById("app-footer");
+  if (!footer) return;
+  const ab = aboutData();
+  const aboutLink = ab
+    ? ` <span class="sep">&#183;</span> <a href="#" onclick="openAbout();return false">${h(ab.title ?? "About")}</a>`
+    : "";
+  footer.innerHTML =
+    `<span>&#169; 2026 Kristian Benestad</span>`
+    + ` <span class="sep">&#183;</span>`
+    + ` <a href="https://docs.benestad.net/invoice" target="_blank" rel="noopener">docs.benestad.net</a>`
+    + ` <span class="sep">&#183;</span>`
+    + ` <a href="https://github.com/kbenestad/invoice" target="_blank" rel="noopener">kbenestad/invoice</a>`
+    + aboutLink;
+}
+
+function openAbout() {
+  const ab = aboutData();
+  if (!ab) return;
+  document.getElementById("about-dialog-header").textContent = ab.title ?? "";
+  document.getElementById("about-dialog-body").innerHTML =
+    typeof marked !== "undefined" ? marked.parse(ab.content ?? "") : h(ab.content ?? "");
+  document.getElementById("about-btn-close").textContent = ab["btn-close"] ?? "Close";
+  document.getElementById("about-modal").style.display = "flex";
+  document.getElementById("about-btn-close").focus();
+}
+
+function closeAbout() {
+  document.getElementById("about-modal").style.display = "none";
+}
+
+document.addEventListener("keydown", e => {
+  if (e.key === "Escape") closeAbout();
+});
+
 // ── Start ─────────────────────────────────────────────────────────────────────
 loadCfg();
 </script>