Task #389: Notification sounds + vibration with per-user customization

DB
- Added user pref columns; vibration is per-channel
  (vibrationEnabledOrder + vibrationEnabledMeeting). Defaults: ding/chime
  sounds, vibration on, mute off. Volume uses the device system level —
  no persisted volume field.

API
- PATCH /auth/me/notification-preferences (requireAuth, whitelisted partial
  update, integer guard for volume). buildAuthUser exposes all new fields.
- OpenAPI spec updated; orval client + zod regenerated.

Frontend
- Static sound library: 8 short WAV assets under public/sounds/ + manifest
  (notification-sound-manifest.ts) mapping id -> labelKey -> URL.
- HTMLAudio-based player (notification-sounds.ts) with throttle, unlock,
  cache, and AUTOPLAY_BLOCKED_EVENT dispatch when play is denied pre-gesture.
- Settings popover: global mute + slot tabs (orders/meetings) with
  per-channel sound + per-channel vibration + per-channel toggle, sound list
  with one-tap previews. Concurrency-safe optimistic updates (monotonic seq
  counter). RTL-correct toggle knob transforms.
- QuickMuteButton: one-tap topbar mute control (Volume2/VolumeX) with
  confirmation toast.
- useAudioUnlock: unlocks audio on first interaction.
- useAutoplayHint: toasts a localized "click anywhere to enable" hint when
  the player reports a blocked play attempt.
- Socket hook plays the right per-channel sound + vibration on
  notification_created (orders, executive_meeting) when the tab is hidden.
- UpcomingMeetingAlert: plays meeting reminder once per new eligible
  meeting (deduped by meetingId, survives 30s polling refetches). Skipped
  when the tab is currently visible — sound only fires when backgrounded.
- AR/EN translations added.

Pre-existing TS errors in executive-meetings.ts (font_settings) and
pre-existing test workflow failures are unrelated.

lib/api-client-react/src/generated/api.schemas.ts

@@ -118,11 +118,6 @@ export interface UpdateNotificationPreferencesBody {
   vibrationEnabledOrder?: boolean;
   vibrationEnabledMeeting?: boolean;
   notificationsMuted?: boolean;
-  /**
-   * @minimum 0
-   * @maximum 100
-   */
-  notificationVolume?: number;
 }
 
 export interface UpdateClockHour12Body {
@@ -164,7 +159,6 @@ export interface AuthUser {
   vibrationEnabledOrder: boolean;
   vibrationEnabledMeeting: boolean;
   notificationsMuted: boolean;
-  notificationVolume: number;
   roles: string[];
   groups: GroupSummary[];
   createdAt: string;