fix: Phase 1 critical+high fixes (17/18 items)

CRITICAL fixes:
- C1: Error swallowing - throw TransportError on network failure in getEmails/searchEmails
- C2: Recurrence expansion ID delimiter changed from ':' to '::occurrence::'
- C3: Cross-account calendar event UID dedup after multi-account aggregation
- C4: Admin session token revocation via JTI blacklist on logout
- C6: FTS5 schema-drop - add warning log for automatic reindex trigger
- C7: Settings lock - gate updateSetting() with isSettingLocked() check
- C8: Offline push pause - add offline event handler that closes push transports

HIGH fixes:
- H1: Push handler - add ContactCard and FileNode branches
- H2: WS fallback - await state snapshot before reconcileAfterWebSocketFallback
- H3: Auth rate limiting - add checkUserAuthRateLimit to session and token routes
- H4: OAuth logs - strip access_token from error log context
- H7: Template XSS - apply DOMPurify to HTML template body on import
- H8: Secure cookie - derive from x-forwarded-proto, not NODE_ENV
- H9: bcrypt fix - remove bcrypt prefixes from isHashed() so scrypt-only
- H13: calendarTasksEnabled - apply admin gate at runtime in calendar page
- H14: Task mutations - add try/catch error handling to update/delete/toggle
- H18: autoSelectReplyIdentity default changed from false to true

Deferred: P1.3 (C5 auth localStorage encryption) - requires custom Zustand persist adapter.

stores/calendar-store.ts

@@ -387,7 +387,16 @@ export const useCalendarStore = create<CalendarStore>()(
               }
             }),
           );
-          set({ events: results.flat(), isLoadingEvents: false, dateRange: { start, end } });
+          const allEvents = results.flat();
+          // Deduplicate cross-account events by uid + recurrenceId
+          const seen = new Set<string>();
+          const deduped = allEvents.filter(e => {
+            const key = `${e.uid || e.id}::${e.recurrenceId || ''}`;
+            if (seen.has(key)) return false;
+            seen.add(key);
+            return true;
+          });
+          set({ events: deduped, isLoadingEvents: false, dateRange: { start, end } });
         } catch (error) {
           debug.error('Failed to fetch all-account events:', error);
           set({ error: 'Failed to load events', isLoadingEvents: false });