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/settings-store.ts

@@ -484,7 +484,7 @@ const DEFAULT_SETTINGS = {
   autoSaveDraftInterval: 60000, // 1 minute
   sendConfirmation: false,
   defaultReplyMode: 'reply' as ReplyMode,
-  autoSelectReplyIdentity: false,
+  autoSelectReplyIdentity: true,
   plainTextMode: false,
   rtlEditingSupport: false,
   subAddressDelimiter: DEFAULT_SUB_ADDRESS_DELIMITER,
@@ -643,7 +643,14 @@ export const useSettingsStore = create<SettingsState>()(
     (set, get) => ({
       ...DEFAULT_SETTINGS,
 
-      updateSetting: (key, value) => {
+      updateSetting: (key, value, opts?: { force?: boolean }) => {
+        if (!opts?.force) {
+          try {
+            const { usePolicyStore } = require('./policy-store');
+            const locked = usePolicyStore.getState().isSettingLocked(key);
+            if (locked) return;
+          } catch { /* policy store may not be loaded yet */ }
+        }
         set({ [key]: value });
 
         // Apply font size to document root