feat(desktop): port v0.11.4-v0.15.2 from Tauri to Electron + Discord-parity audio (v0.16.0)

Chronological port of every Tauri release commit (v0.11.4 -> v0.15.2)
into the Electron rebuild, plus Discord-style audio handling that goes
beyond the Tauri original.

Highlights:
  - All 17 Tauri release commits ported (audio fixes, custom notification
    sound, Discord-style chat UX, profile banner, changelog page,
    Discord-parity call UX, screen-share echo + re-watch UX, audio-loop
    fix).
  - Native napi-rs audio-loopback addon with WASAPI process-loopback:
      * EXCLUDE_TARGET_PROCESS_TREE for full-screen shares -> peers
        never hear themselves echoed back through the capture.
      * INCLUDE_TARGET_PROCESS_TREE for window shares -> only the
        picked window's audio is captured, not the whole OS mixer
        (Discord parity).
      * HWND -> PID resolution via Win32 GetWindowThreadProcessId.
  - Discord-style screen-source picker (thumbnail grid, screens vs
    apps tabs, live-refreshing thumbnails).
  - Hash routing fix for packaged builds (file:// can't resolve
    BrowserRouter paths).
  - Tauri sources removed (apps/desktop/src-tauri).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/desktop/src/context/AuthContext.tsx

@@ -3,6 +3,7 @@ import {
   getOwnProfile,
   signOut as supabaseSignOut,
   type Profile,
+  touchDeviceLastSeen,
   updateOwnProfile,
 } from '@chat-app/shared/auth';
 import { changeLocale, isSupportedLocale } from '@chat-app/shared/i18n';
@@ -14,11 +15,13 @@ import {
   useContext,
   useEffect,
   useMemo,
+  useRef,
   useState,
 } from 'react';
 import { useTranslation } from 'react-i18next';
 
 import { findExistingDevice } from '../lib/device';
+import { PRESENCE_HEARTBEAT_MS } from '../lib/presence';
 import { setSecretStoreUser } from '../lib/secretStore';
 import { supabase } from '../lib/supabase';
 import { registerWebPush } from '../lib/webPush';
@@ -46,6 +49,7 @@ export function AuthProvider({ children }: { children: ReactNode }) {
   const [profile, setProfile] = useState<Profile | null>(null);
   const [device, setDevice] = useState<DeviceRecord | null>(null);
   const [deviceLookupDone, setDeviceLookupDone] = useState(false);
+  const autoOnlineUserRef = useRef<string | null>(null);
 
   // Initial session + auth subscription. We verify the cached JWT against the
   // server (via getUser) once on mount. Only purge the session on an
@@ -154,8 +158,14 @@ export function AuthProvider({ children }: { children: ReactNode }) {
   //   request usually slips through; the next page load corrects state if it
   //   didn't.
   useEffect(() => {
-    if (!session || !profile) return;
-    if (profile.presenceState === 'offline') {
+    if (!session) {
+      autoOnlineUserRef.current = null;
+      return;
+    }
+    if (!profile) return;
+    const shouldApplyInitialAutoOnline = autoOnlineUserRef.current !== session.user.id;
+    autoOnlineUserRef.current = session.user.id;
+    if (profile.presenceState === 'offline' && shouldApplyInitialAutoOnline) {
       void updateOwnProfile(supabase, { presenceState: 'online' })
         .then(() => refreshProfile())
         .catch((err: unknown) => {
@@ -165,10 +175,7 @@ export function AuthProvider({ children }: { children: ReactNode }) {
     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'
-      ) {
+      if (profile.presenceState !== 'online' && profile.presenceState !== 'offline') {
         return;
       }
       void updateOwnProfile(supabase, { presenceState: 'offline' }).catch(() => {});
@@ -181,7 +188,36 @@ export function AuthProvider({ children }: { children: ReactNode }) {
     };
   }, [session, profile, refreshProfile]);
 
+  useEffect(() => {
+    if (!session || !device?.id) return;
+
+    const touch = () => {
+      void touchDeviceLastSeen(supabase, device.id).catch((err: unknown) => {
+        console.warn('presence heartbeat failed', err);
+      });
+    };
+    const touchWhenVisible = () => {
+      if (document.visibilityState === 'visible') touch();
+    };
+
+    touch();
+    const heartbeat = window.setInterval(touch, PRESENCE_HEARTBEAT_MS);
+    window.addEventListener('focus', touch);
+    window.addEventListener('online', touch);
+    document.addEventListener('visibilitychange', touchWhenVisible);
+
+    return () => {
+      window.clearInterval(heartbeat);
+      window.removeEventListener('focus', touch);
+      window.removeEventListener('online', touch);
+      document.removeEventListener('visibilitychange', touchWhenVisible);
+    };
+  }, [session, device?.id]);
+
   const signOut = useCallback(async () => {
+    await updateOwnProfile(supabase, { presenceState: 'offline' }).catch((err: unknown) => {
+      console.warn('offline update before sign-out failed', err);
+    });
     await supabaseSignOut(supabase);
   }, []);