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/lib/liveCaptions.ts

@@ -0,0 +1,119 @@
+// Discord-style live captions. Uses the browser's SpeechRecognition API to
+// transcribe the LOCAL user's mic, then broadcasts each interim/final result
+// to peers via the LiveKit DataChannel. Receivers store and display them.
+//
+// Privacy note: speech recognition runs in the browser. On Chromium-based
+// runtimes (incl. Tauri's WebView2 on Windows) this calls into the browser's
+// own engine, which today reaches Google's cloud — same trade-off as Discord.
+// We ship a hard off switch and require an explicit user toggle.
+
+const STORAGE_KEY = 'chatapp.liveCaptions.v1';
+
+export interface LiveCaptionsSettings {
+  enabled: boolean;
+  /** BCP-47 language tag, e.g. "de-DE" or "en-US". Auto-detect uses navigator.language. */
+  lang: string | null;
+}
+
+const DEFAULTS: LiveCaptionsSettings = {
+  enabled: false,
+  lang: null,
+};
+
+type Listener = (s: LiveCaptionsSettings) => void;
+const listeners = new Set<Listener>();
+let cached: LiveCaptionsSettings | null = null;
+
+function read(): LiveCaptionsSettings {
+  if (cached) return cached;
+  try {
+    const raw = window.localStorage.getItem(STORAGE_KEY);
+    if (!raw) {
+      cached = DEFAULTS;
+      return cached;
+    }
+    const parsed = JSON.parse(raw) as Partial<LiveCaptionsSettings>;
+    cached = {
+      enabled: typeof parsed.enabled === 'boolean' ? parsed.enabled : DEFAULTS.enabled,
+      lang:
+        typeof parsed.lang === 'string' && parsed.lang.length > 0
+          ? parsed.lang
+          : DEFAULTS.lang,
+    };
+    return cached;
+  } catch {
+    cached = DEFAULTS;
+    return cached;
+  }
+}
+
+function write(s: LiveCaptionsSettings): void {
+  cached = s;
+  try {
+    window.localStorage.setItem(STORAGE_KEY, JSON.stringify(s));
+  } catch {
+    /* quota / private mode */
+  }
+  for (const l of listeners) l(s);
+}
+
+export function getLiveCaptionsSettings(): LiveCaptionsSettings {
+  return read();
+}
+
+export function updateLiveCaptionsSettings(
+  patch: Partial<LiveCaptionsSettings>,
+): LiveCaptionsSettings {
+  const next = { ...read(), ...patch };
+  write(next);
+  return next;
+}
+
+export function subscribeLiveCaptionsSettings(listener: Listener): () => void {
+  listeners.add(listener);
+  return () => listeners.delete(listener);
+}
+
+// Browser feature-detect. Chromium ships under both names; Firefox lacks it
+// outright. Returns the constructor or null.
+type SpeechRecognitionCtor = new () => SpeechRecognitionLike;
+interface SpeechRecognitionLike extends EventTarget {
+  continuous: boolean;
+  interimResults: boolean;
+  lang: string;
+  start: () => void;
+  stop: () => void;
+  abort: () => void;
+  onresult: ((e: SpeechRecognitionEventLike) => void) | null;
+  onerror: ((e: SpeechRecognitionErrorLike) => void) | null;
+  onend: (() => void) | null;
+}
+interface SpeechRecognitionEventLike {
+  resultIndex: number;
+  results: ArrayLike<{
+    isFinal: boolean;
+    [index: number]: { transcript: string };
+    length: number;
+  }>;
+}
+interface SpeechRecognitionErrorLike {
+  error: string;
+}
+
+export function getSpeechRecognitionCtor(): SpeechRecognitionCtor | null {
+  const w = window as unknown as {
+    SpeechRecognition?: SpeechRecognitionCtor;
+    webkitSpeechRecognition?: SpeechRecognitionCtor;
+  };
+  return w.SpeechRecognition ?? w.webkitSpeechRecognition ?? null;
+}
+
+export function isLiveCaptionsSupported(): boolean {
+  return getSpeechRecognitionCtor() !== null;
+}
+
+export type {
+  SpeechRecognitionLike,
+  SpeechRecognitionEventLike,
+  SpeechRecognitionErrorLike,
+};