feat(voice): per-account choice between Whisper and the browser; STT_ALLOW_BROWSER

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/lib/voice.ts

@@ -3,6 +3,8 @@
 //   server   record with MediaRecorder, the own Whisper server turns it into text after stopping
 //   browser  the browser's speech recognition (Chrome, Edge, Safari; text appears while speaking)
 //   off      no voice input
+// With a Whisper server everyone may pick the browser instead (account setting), unless the server
+// forbids it (STT_ALLOW_BROWSER=false).
 import { api } from './api';
 import type { VoiceMode } from './types';
 
@@ -15,6 +17,33 @@ export interface VoiceConfig {
 
 let configPromise: Promise<VoiceConfig> | null = null;
 let loadedConfig: VoiceConfig | null = null;
+let serverMode: VoiceMode | undefined;
+let browserAllowed = true;
+let preference: '' | 'browser' = '';
+
+/** Fired when the effective mode changes (the account setting was loaded or changed). */
+export const VOICE_CONFIG_EVENT = 'mindsift:voice-config';
+
+function applyPreference(mode: VoiceMode | undefined): VoiceMode | undefined {
+  return mode === 'server' && browserAllowed && preference === 'browser' ? 'browser' : mode;
+}
+
+/** The account's choice ('' = Whisper server, 'browser'); set when the user is loaded or changes it. */
+export function setVoicePreference(next: '' | 'browser' | undefined): void {
+  const value = next === 'browser' ? 'browser' : '';
+  if (value === preference) return;
+  preference = value;
+  if (loadedConfig) {
+    loadedConfig = { ...loadedConfig, mode: effectiveMode(applyPreference(serverMode)) };
+    configPromise = Promise.resolve(loadedConfig);
+  }
+  if (typeof window !== 'undefined') window.dispatchEvent(new CustomEvent(VOICE_CONFIG_EVENT));
+}
+
+/** Whether the account may choose between the Whisper server and the browser. */
+export function voiceChoiceAvailable(): boolean {
+  return serverMode === 'server' && browserAllowed;
+}
 
 export function browserRecognition(): any {
   if (typeof window === 'undefined') return null;
@@ -38,7 +67,9 @@ export function loadVoiceConfig(): Promise<VoiceConfig> {
     configPromise = api
       .getAuthStatus()
       .then((st) => {
-        loadedConfig = { mode: effectiveMode(st.voice?.mode), maxSeconds: st.voice?.maxSeconds || 600 };
+        serverMode = st.voice?.mode;
+        browserAllowed = st.voice?.browserAllowed !== false;
+        loadedConfig = { mode: effectiveMode(applyPreference(serverMode)), maxSeconds: st.voice?.maxSeconds || 600 };
         return loadedConfig;
       })
       .catch(() => {
@@ -58,6 +89,9 @@ export function currentVoiceConfig(): VoiceConfig {
 export function resetVoiceConfig(): void {
   configPromise = null;
   loadedConfig = null;
+  serverMode = undefined;
+  browserAllowed = true;
+  preference = '';
 }
 
 // Containers in order of preference; Safari only records MP4/AAC