feat: voice messages, offline queue, delivery ticks, volume slider, admin + scaling

- Voice messages: MediaRecorder → encrypted attachment, custom waveform
  player via OfflineAudioContext, 60s limit + live mic-level meter
- Offline message queue: localStorage outbox, exponential backoff retries,
  optimistic pending bubble with retry/discard
- Delivery indicator: message_deliveries table + RLS (reciprocal receipts),
  ✓ / ✓✓ / ✓✓-blue tick states, group-aware (all members must ack)
- Per-participant volume slider in calls via right-click tile menu,
  persisted to localStorage, applied to attached audio elements
- Group call scaling: grid up to 12 tiles with pagination,
  active-speaker auto-promotion in fullscreen
- Push notifications scaffolding: service worker, VAPID subscription
  registration, notify-push edge function skeleton
- Backup recovery code: 24-char base32 code (~120 bits entropy) as
  alternative decrypt path, restore UI with mode toggle
- Admin panel: conversations list, audit log (admin_audit_log table +
  admin_log_action RPC), audit entry on user flag toggle
- Search v2: sender filter, attachment-only toggle, date range
- Reactions pop animation (scale 0.4→1.15→1 on count change)
- Message list windowing (150 default, expand via IntersectionObserver)
- Stub cleanup: removed dead ScreenshareStub from CallParticipantTile

Fixes:
- Focus-triggered flicker: dropped window.focus listeners in three spots,
  throttled visibilitychange/online wake-refreshes to 30s, keep existing
  data visible during background re-syncs (no more spinner on every click)
- Voice attachment audio element collapsed to 0px on peer side — now
  forces 280px min-width on bubble

Migrations (push required):
  20260421000001_message_deliveries.sql
  20260421000002_admin_audit_log.sql

Server TODO:
  VAPID keys + notify-push edge function deploy

apps/desktop/tailwind.config.js

@@ -74,6 +74,7 @@ export default {
         'live-dot': 'liveDotPulse 1.5s ease-in-out infinite',
         'slide-in-call': 'slideInCall 0.4s cubic-bezier(0.22,1,0.36,1)',
         'fs-hint': 'fsHintFade 3.5s ease-out forwards',
+        'reaction-pop': 'reactionPop 220ms cubic-bezier(0.34, 1.56, 0.64, 1)',
       },
       keyframes: {
         blob: {
@@ -110,6 +111,11 @@ export default {
           '15%, 75%': { opacity: '1', transform: 'translate(-50%, 0)' },
           '100%': { opacity: '0', transform: 'translate(-50%, -6px)' },
         },
+        reactionPop: {
+          '0%': { opacity: '0', transform: 'scale(0.4)' },
+          '70%': { opacity: '1', transform: 'scale(1.15)' },
+          '100%': { opacity: '1', transform: 'scale(1)' },
+        },
       },
       boxShadow: {
         glow: '0 0 40px -8px rgba(99, 102, 241, 0.35)',