242f63ab26
- DB: 7 new user prefs (sound per slot, per-type toggles, vibration, mute, volume). - API: PATCH /auth/me/notification-preferences with whitelisted partial update, integer guard for volume, and hydrated AuthUser response. AuthUser now exposes the 7 new fields. - Frontend: Web Audio synth library (8 sounds), settings popover with global mute/vibration/volume/per-type toggles, slot tabs, sound preview buttons, shift+click on bell for quick mute. Concurrency-safe optimistic updates with monotonic seq counter. RTL-correct toggle knob transforms. - Socket hook plays sound on notification_created (orders/meetings only) when tab is hidden, respecting global mute and per-type toggles. - Audio unlock hook mounted globally to satisfy autoplay restrictions. - AR/EN translations added. Pre-existing TS errors in executive-meetings.ts (font_settings) and pre-existing test failures in test workflow are unrelated to this task.