feat: file variety, user status, DND gate, drag-drop, mentions, link preview, emoji picker, soundboard, ringtone

Attachments
- Video: native <video controls>, decrypted blob, metadata preload
- PDF: collapsible <object> viewer with download + preview toggle
- Generic: file card with lazy decrypt, mime-to-extension map
- MessageBubble dispatch: audio/image/video/pdf/generic by mime
- Composer accept widened from image/* to any; AttachmentPreview renders
  non-images as file cards

User status
- usePeerPresence returns { state, statusMessage } and tracks both fields
  via realtime updates
- ConversationHeader subtitle shows custom status_message when peer is
  online/idle/dnd (with message set); falls back to localized presence
  label; always "Offline" when state === 'offline'
- UserBar: status_message input in dropdown (max 128 chars, save on
  blur/Enter), subtitle uses same precedence as peer view
- AuthContext: auto-flip offline → online on session mount; best-effort
  offline on beforeunload/pagehide; respects explicit idle/dnd/invisible
- i18n: presence.status_placeholder (DE + EN)

DND
- CallUI: incoming ring suppressed when own presence === 'dnd' (outgoing
  rings stay audible — user-initiated)
- CallContext: presenceRef mirrors profile.presenceState, incoming-call
  and missed-call OS notifications skipped under DND
- ConversationsContext already gated message tone + notify

Drag/drop + paste
- Page-root drag handlers feed ingestFiles; overlay shown while dragging
- Textarea onPaste extracts clipboard image items

@mentions in groups
- MentionAutocomplete: keyboard-driven dropdown, arrow/enter/tab/esc
- Composer onChange parses trailing @token, auto-open
- renderBodyWithMentions highlights @username tokens in bubbles

Link previews
- Migration 20260421000003_link_previews.sql (cache table, auth read,
  service-role write via edge function)
- Edge function og-preview: POST {url}, fetches HTML (6s timeout, 1MB
  cap), regex-parses OG/twitter/description, upserts cache
- useLinkPreview hook with in-memory cache + inflight dedup
- LinkPreviewCard rendered from first URL in message body

Emoji picker
- Built-in curated set (~250 emojis) across five categories
- Search by keyword/emoji char/category, recent list persisted in
  localStorage
- Trigger button next to + and voice buttons in composer

Soundboard + ringtone + mic pipeline
- Pulled in (user-authored) SoundboardManagerDialog/Panel/Settings,
  RingtoneSettings, mic pipeline + hotkeys + storage modules
- AuthContext imports updateOwnProfile for presence auto-flip

Fixes
- AttachmentAudio min-width so bubbles don't collapse to 0px on peer
  side
- Focus flicker: visibility/online wake refresh throttled to 30s,
  focus listener dropped, loading flag only on first fetch

apps/desktop/src/context/AuthContext.tsx

@@ -3,6 +3,7 @@ import {
   getOwnProfile,
   signOut as supabaseSignOut,
   type Profile,
+  updateOwnProfile,
 } from '@chat-app/shared/auth';
 import { changeLocale, isSupportedLocale } from '@chat-app/shared/i18n';
 import type { Session } from '@supabase/supabase-js';
@@ -143,6 +144,43 @@ export function AuthProvider({ children }: { children: ReactNode }) {
     void registerWebPush(device.id);
   }, [device?.id]);
 
+  // Auto online/offline transition.
+  //
+  // - On mount with a session whose last persisted state is `offline`, flip
+  //   to `online`. We never override an explicit `idle`, `dnd`, or
+  //   `invisible` choice — those are user intent.
+  // - On `pagehide` / `beforeunload`, fire a best-effort update to
+  //   `offline`. Browsers don't guarantee delivery during unload, but the
+  //   request usually slips through; the next page load corrects state if it
+  //   didn't.
+  useEffect(() => {
+    if (!session || !profile) return;
+    if (profile.presenceState === 'offline') {
+      void updateOwnProfile(supabase, { presenceState: 'online' })
+        .then(() => refreshProfile())
+        .catch((err: unknown) => {
+          console.warn('auto online flip failed', err);
+        });
+    }
+    const onLeave = () => {
+      // Skip if user explicitly chose a non-online state — they probably
+      // want to look unavailable on next reconnect too.
+      if (
+        profile.presenceState !== 'online' &&
+        profile.presenceState !== 'offline'
+      ) {
+        return;
+      }
+      void updateOwnProfile(supabase, { presenceState: 'offline' }).catch(() => {});
+    };
+    window.addEventListener('beforeunload', onLeave);
+    window.addEventListener('pagehide', onLeave);
+    return () => {
+      window.removeEventListener('beforeunload', onLeave);
+      window.removeEventListener('pagehide', onLeave);
+    };
+  }, [session, profile, refreshProfile]);
+
   const signOut = useCallback(async () => {
     await supabaseSignOut(supabase);
   }, []);