Fix period initialisation order so first expense line date defaults correctly

state.periodFrom was set inside render(), after newItem() was called,
so the first line always got an empty date. Setting the period before
pushing the first item ensures the default date is the period start.

https://claude.ai/code/session_01MbwfxnjLA9KdFTrfzB55HM

app/index.html

@@ -1017,6 +1017,9 @@ async function init() {
   try {
     await loadConfig();
     state.baseCurrency = CFG['currency-base'];
+    const p = defaultPeriod();
+    state.periodFrom = p.from;
+    state.periodTo = p.to;
     state.items.push(newItem());
     render();
   } catch (e) {