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/electron/modules/notifications.ts

@@ -0,0 +1,26 @@
+// OS notifications. Electron's Notification API doesn't have a separate
+// permission prompt on desktop — permission is implicit and always
+// granted — so `notify:permission` is a compatibility shim that keeps
+// the renderer's existing plugin-notification call-sites working
+// without branching.
+
+import { ipcMain, Notification } from 'electron';
+
+import { CHANNELS, type NotifyArgs } from '../ipc-types';
+
+export function register(): void {
+  ipcMain.handle(CHANNELS.NOTIFY_SHOW, async (_evt, args: NotifyArgs): Promise<void> => {
+    if (!Notification.isSupported()) return;
+    const n = new Notification({
+      title: args.title,
+      body: args.body,
+      silent: args.silent ?? true,
+    });
+    n.show();
+  });
+
+  ipcMain.handle(
+    CHANNELS.NOTIFY_PERMISSION,
+    async (): Promise<'granted' | 'denied' | 'default'> => 'granted',
+  );
+}