feat(voice): all microphone buttons use the server's speech recognition

- New useVoiceInput hook (lib/voice.ts): "server" records with MediaRecorder
  and sends to /voice/transcribe, "browser" keeps the live recognition,
  "off" or missing browser support hides the microphone.
- Quick dump bar, mobile capture sheet and hold-to-record use it; live
  waves from the real input level (VoiceWave) and "Wird erkannt…".
- Recordings stop after STT_MAX_SECONDS.

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

frontend/src/lib/voice.ts

@@ -0,0 +1,157 @@
+// Voice input for all places with a microphone button. The server decides how it works (STT_* in the
+// environment, reported by /auth/status):
+//   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
+import { api } from './api';
+import type { VoiceMode } from './types';
+
+export type EffectiveVoiceMode = VoiceMode | 'unsupported';
+
+export interface VoiceConfig {
+  mode: EffectiveVoiceMode;
+  maxSeconds: number;
+}
+
+let configPromise: Promise<VoiceConfig> | null = null;
+let loadedConfig: VoiceConfig | null = null;
+
+export function browserRecognition(): any {
+  if (typeof window === 'undefined') return null;
+  return (window as any).SpeechRecognition || (window as any).webkitSpeechRecognition || null;
+}
+
+export function canRecord(): boolean {
+  return typeof window !== 'undefined' && typeof (window as any).MediaRecorder !== 'undefined' && !!navigator.mediaDevices?.getUserMedia;
+}
+
+/** What this browser can actually do with the server's setting. */
+export function effectiveMode(mode: VoiceMode | undefined): EffectiveVoiceMode {
+  if (mode === 'off') return 'off';
+  if (mode === 'server') return canRecord() ? 'server' : 'unsupported';
+  return browserRecognition() ? 'browser' : 'unsupported';
+}
+
+/** Loaded once per page; the setting only changes with a server restart. */
+export function loadVoiceConfig(): Promise<VoiceConfig> {
+  if (!configPromise) {
+    configPromise = api
+      .getAuthStatus()
+      .then((st) => {
+        loadedConfig = { mode: effectiveMode(st.voice?.mode), maxSeconds: st.voice?.maxSeconds || 600 };
+        return loadedConfig;
+      })
+      .catch(() => {
+        configPromise = null; // offline at start: ask again next time
+        return { mode: effectiveMode('browser'), maxSeconds: 600 };
+      });
+  }
+  return configPromise;
+}
+
+/** The setting if already loaded; until then the browser's recognition (a button must react at once). */
+export function currentVoiceConfig(): VoiceConfig {
+  return loadedConfig ?? { mode: effectiveMode('browser'), maxSeconds: 600 };
+}
+
+/** For tests. */
+export function resetVoiceConfig(): void {
+  configPromise = null;
+  loadedConfig = null;
+}
+
+// Containers in order of preference; Safari only records MP4/AAC
+const RECORDING_TYPES = ['audio/webm;codecs=opus', 'audio/webm', 'audio/mp4', 'audio/ogg;codecs=opus'];
+
+function recordingType(): string | undefined {
+  const MR = (window as any).MediaRecorder;
+  if (!MR?.isTypeSupported) return undefined;
+  return RECORDING_TYPES.find((t) => MR.isTypeSupported(t));
+}
+
+/**
+ * One recording from the microphone, with a live input level for wave animations. stop() resolves
+ * with the audio; cancel() throws it away.
+ */
+export class VoiceRecorder {
+  private stream: MediaStream | null = null;
+  private recorder: MediaRecorder | null = null;
+  private chunks: Blob[] = [];
+  private audioCtx: AudioContext | null = null;
+  private analyser: AnalyserNode | null = null;
+  private samples: Uint8Array | null = null;
+  private done: ((blob: Blob | null) => void) | null = null;
+
+  async start(): Promise<void> {
+    this.stream = await navigator.mediaDevices.getUserMedia({
+      audio: { echoCancellation: true, noiseSuppression: true, autoGainControl: true },
+    });
+    const type = recordingType();
+    this.recorder = new MediaRecorder(this.stream, type ? { mimeType: type } : undefined);
+    this.chunks = [];
+    this.recorder.ondataavailable = (e) => {
+      if (e.data.size > 0) this.chunks.push(e.data);
+    };
+    this.recorder.onstop = () => {
+      const blob = this.chunks.length ? new Blob(this.chunks, { type: this.recorder?.mimeType || type || 'audio/webm' }) : null;
+      this.release();
+      this.done?.(blob);
+      this.done = null;
+    };
+    this.recorder.start(1000);
+    try {
+      const Ctx = (window as any).AudioContext || (window as any).webkitAudioContext;
+      this.audioCtx = new Ctx();
+      const source = this.audioCtx!.createMediaStreamSource(this.stream);
+      this.analyser = this.audioCtx!.createAnalyser();
+      this.analyser.fftSize = 512;
+      source.connect(this.analyser);
+      this.samples = new Uint8Array(this.analyser.fftSize);
+      void this.audioCtx!.resume?.();
+    } catch {
+      this.analyser = null; // no level, the recording still works
+    }
+  }
+
+  /** Input level 0..1 (roughly loudness), or null when unknown. */
+  level(): number | null {
+    if (!this.analyser || !this.samples) return null;
+    this.analyser.getByteTimeDomainData(this.samples as Uint8Array<ArrayBuffer>);
+    let sum = 0;
+    for (const v of this.samples) {
+      const x = (v - 128) / 128;
+      sum += x * x;
+    }
+    return Math.min(1, Math.sqrt(sum / this.samples.length) * 4);
+  }
+
+  stop(): Promise<Blob | null> {
+    return new Promise((resolve) => {
+      if (!this.recorder || this.recorder.state === 'inactive') {
+        this.release();
+        resolve(null);
+        return;
+      }
+      this.done = resolve;
+      this.recorder.stop();
+    });
+  }
+
+  cancel(): void {
+    this.done = null;
+    if (this.recorder && this.recorder.state !== 'inactive') {
+      this.recorder.onstop = () => this.release();
+      this.recorder.stop();
+    } else {
+      this.release();
+    }
+  }
+
+  private release(): void {
+    this.stream?.getTracks().forEach((t) => t.stop());
+    this.stream = null;
+    void this.audioCtx?.close?.().catch(() => {});
+    this.audioCtx = null;
+    this.analyser = null;
+  }
+}