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/tray.ts

@@ -0,0 +1,109 @@
+// System tray + Windows taskbar overlay badge. Renderer pushes the
+// current aggregate unread count via CHANNELS.TRAY_UNREAD; we update the
+// tooltip and (on Windows) set an overlay icon on the main window's
+// taskbar button.
+//
+// Overlay image is a pre-rendered 16x16 red dot embedded as base64 so
+// the module is self-contained — no runtime canvas dependency.
+
+import {
+  app,
+  BrowserWindow,
+  ipcMain,
+  Menu,
+  nativeImage,
+  type NativeImage,
+  Tray,
+} from 'electron';
+import path from 'node:path';
+
+import { CHANNELS } from '../ipc-types';
+
+let trayRef: Tray | null = null;
+let overlayImage: NativeImage | null = null;
+
+function resolveIconPath(): string {
+  return path.join(process.resourcesPath || app.getAppPath(), 'icon.ico');
+}
+
+function resolveIconPathDev(): string {
+  return path.join(app.getAppPath(), 'resources', 'icon.ico');
+}
+
+function loadTrayIcon(): NativeImage {
+  for (const p of [resolveIconPath(), resolveIconPathDev()]) {
+    try {
+      const img = nativeImage.createFromPath(p);
+      if (!img.isEmpty()) return img;
+    } catch {
+      /* try next */
+    }
+  }
+  return nativeImage.createEmpty();
+}
+
+function buildOverlay(): NativeImage {
+  if (overlayImage) return overlayImage;
+  // 16x16 PNG, solid red circle. Inline base64 so no external file lookup.
+  const base64 =
+    'iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAAPElEQVR42mNkYGD4z0AGYBxVSF2F//' +
+    '//Z2BgYGD4/58kBYz4FDAxMDAwMDIwMDD8//+foArGUYWjCoc1AABTgwUBf3lZtAAAAABJRU5ErkJggg==';
+  overlayImage = nativeImage.createFromBuffer(Buffer.from(base64, 'base64'));
+  return overlayImage;
+}
+
+export function register(mainWindow: BrowserWindow): void {
+  const icon = loadTrayIcon();
+  trayRef = new Tray(icon.isEmpty() ? nativeImage.createEmpty() : icon);
+  trayRef.setToolTip('ChatApp');
+
+  const menu = Menu.buildFromTemplate([
+    {
+      label: 'Open',
+      click: (): void => {
+        if (mainWindow.isDestroyed()) return;
+        if (mainWindow.isMinimized()) mainWindow.restore();
+        mainWindow.show();
+        mainWindow.focus();
+      },
+    },
+    { type: 'separator' },
+    {
+      label: 'Quit',
+      click: (): void => {
+        app.quit();
+      },
+    },
+  ]);
+  trayRef.setContextMenu(menu);
+  trayRef.on('click', (): void => {
+    if (mainWindow.isDestroyed()) return;
+    if (mainWindow.isMinimized()) mainWindow.restore();
+    if (mainWindow.isVisible()) mainWindow.focus();
+    else mainWindow.show();
+  });
+
+  ipcMain.handle(CHANNELS.TRAY_UNREAD, async (_evt, count: number): Promise<void> => {
+    const n = Math.max(0, Math.floor(Number(count) || 0));
+    if (trayRef && !trayRef.isDestroyed()) {
+      trayRef.setToolTip(n > 0 ? `ChatApp — ${n} unread` : 'ChatApp');
+    }
+    if (mainWindow.isDestroyed()) return;
+    if (process.platform === 'win32') {
+      if (n > 0) {
+        mainWindow.setOverlayIcon(buildOverlay(), `${n} unread`);
+      } else {
+        mainWindow.setOverlayIcon(null, '');
+      }
+    }
+  });
+
+  app.on('before-quit', () => {
+    try {
+      trayRef?.destroy();
+    } catch {
+      /* already gone */
+    }
+    trayRef = null;
+  });
+}