Fix period-filter dropdown permanently stuck on empty options

loadPendingPeriods() cached its result via a one-shot periodsReady flag
that, once true, was never reset except by a Manage Periods save. If
the dropdown got focused before the citizen list's first load finished
(e.g. right after login, made more likely by the recent debounce added
to refreshDashboard), it would compute against an empty allCitizens,
find no periods, and set periodsReady=true anyway -- permanently
showing only "All pending (any period)" for the rest of the session,
even once the real data arrived.

refreshDashboard now resets periodsReady/unpaidCache every time it
repopulates allCitizens, so the next dropdown focus (or an
already-active period filter) recomputes against current data instead
of being stuck on a stale/empty snapshot.

Author: claude

index.html

@@ -1174,6 +1174,16 @@ <h4>Pending UPI payments <span id="pendingCount" class="pending-badge">0</span><
   }
   if(seq !== dashboardRefreshSeq) return; // superseded by a newer refresh; drop this stale result
   allCitizens = list;
+  // The period dropdown's cache (unpaidCache/periodsReady) was built from
+  // whatever allCitizens looked like at the time it was requested. If that
+  // happened before the very first citizen list arrived (e.g. someone opens
+  // the dropdown right after login), it would otherwise permanently cache an
+  // empty result — periodsReady stays true forever with no periods listed.
+  // Invalidating it here means the next dropdown focus (or an already-active
+  // period filter, re-checked by renderList below) recomputes against
+  // current data instead of a possibly-stale/empty snapshot.
+  periodsReady = false;
+  unpaidCache = new Map();
   renderStats(); renderList(); refreshPending();
 }
 function renderStats(){