feat(workspace): voice notes via /audio (M3)

- /audio (only in an empty bullet) shows a recording bubble: green round
  button starts, it turns red with a live wave and timer on its left, a
  tap saves the recording as an inline audio player. An audio file can be
  uploaded instead; Esc/✕ restores the empty bullet.
- Chrome's WebM recordings get their length measured, so the player shows
  the total time and seeking works.
- With the own Whisper server "Transkribieren" turns the recording into
  the (searchable) caption.
- Loaded files keep their Blob, as the CSP rightly blocks fetch() on blob:
  URLs.

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

frontend/src/features/workspace/AudioRecorderPicker.tsx

@@ -0,0 +1,183 @@
+import React, { useEffect, useRef, useState } from 'react';
+import { Loader2, Mic, Square, Upload, X } from 'lucide-react';
+import { UploadedMedia, uploadMedia } from '../../lib/media';
+import { VoiceRecorder } from '../../lib/voice';
+import { VoiceWave } from '../../components/VoiceWave';
+import { triggerHaptic } from '../../lib/api';
+
+interface AudioRecorderPickerProps {
+  docId: string;
+  onDone: (media: UploadedMedia) => void;
+  onCancel: () => void;
+}
+
+const MAX_RECORDING_MS = 30 * 60 * 1000;
+
+function formatTime(ms: number): string {
+  const s = Math.floor(ms / 1000);
+  return `${Math.floor(s / 60)}:${String(s % 60).padStart(2, '0')}`;
+}
+
+// Inline bubble an empty bullet turns into after /audio. Green button = start, red button = stop and
+// save; the live wave runs left of the red button. An existing audio file can be uploaded instead.
+export const AudioRecorderPicker: React.FC<AudioRecorderPickerProps> = ({ docId, onDone, onCancel }) => {
+  const [state, setState] = useState<'ready' | 'recording' | 'uploading'>('ready');
+  const [elapsed, setElapsed] = useState(0);
+  const [error, setError] = useState<string | null>(null);
+  const recorderRef = useRef<VoiceRecorder | null>(null);
+  const startedRef = useRef(0);
+  const tickRef = useRef<number | null>(null);
+  const fileRef = useRef<HTMLInputElement>(null);
+  const boxRef = useRef<HTMLDivElement>(null);
+
+  const stopTicking = () => {
+    if (tickRef.current !== null) window.clearInterval(tickRef.current);
+    tickRef.current = null;
+  };
+
+  useEffect(() => {
+    boxRef.current?.focus();
+    return () => {
+      stopTicking();
+      recorderRef.current?.cancel();
+    };
+  }, []);
+
+  const upload = async (blob: Blob, name: string) => {
+    setState('uploading');
+    setError(null);
+    try {
+      onDone(await uploadMedia(docId, blob, name));
+    } catch (err: any) {
+      setError(err?.message || 'Hochladen fehlgeschlagen');
+      setState('ready');
+    }
+  };
+
+  const stop = async () => {
+    const rec = recorderRef.current;
+    if (!rec) return;
+    recorderRef.current = null;
+    stopTicking();
+    triggerHaptic(20);
+    const blob = await rec.stop();
+    if (!blob) {
+      setError('Die Aufnahme ist leer');
+      setState('ready');
+      return;
+    }
+    const ext = blob.type.includes('mp4') ? 'm4a' : blob.type.includes('ogg') ? 'ogg' : 'webm';
+    await upload(blob, `sprachnotiz.${ext}`);
+  };
+
+  const start = async () => {
+    setError(null);
+    const rec = new VoiceRecorder();
+    try {
+      await rec.start();
+    } catch {
+      setError('Kein Zugriff auf das Mikrofon (Berechtigung, oder die Seite läuft nicht über HTTPS)');
+      return;
+    }
+    recorderRef.current = rec;
+    startedRef.current = Date.now();
+    setElapsed(0);
+    setState('recording');
+    triggerHaptic([15, 60, 25]);
+    tickRef.current = window.setInterval(() => {
+      const ms = Date.now() - startedRef.current;
+      setElapsed(ms);
+      if (ms >= MAX_RECORDING_MS) void stop();
+    }, 250);
+  };
+
+  const cancel = () => {
+    stopTicking();
+    recorderRef.current?.cancel();
+    recorderRef.current = null;
+    onCancel();
+  };
+
+  return (
+    <div
+      ref={boxRef}
+      tabIndex={-1}
+      onKeyDown={(e) => {
+        if (e.key === 'Escape') {
+          e.preventDefault();
+          cancel();
+        }
+      }}
+      className="my-1 inline-flex max-w-full flex-col gap-2 rounded-card border border-border bg-panel-elevated px-3 py-2 focus:outline-none"
+    >
+      <div className="flex items-center gap-3">
+        {state === 'recording' && (
+          <>
+            <span className="text-xs font-mono text-main tabular-nums">{formatTime(elapsed)}</span>
+            <VoiceWave getLevel={() => recorderRef.current?.level() ?? null} bars={11} className="h-6 text-status-err" />
+          </>
+        )}
+        {state === 'ready' && <span className="text-xs text-muted">Sprachnotiz aufnehmen</span>}
+        {state === 'uploading' && (
+          <span className="text-xs text-muted flex items-center gap-1.5">
+            <Loader2 className="w-3.5 h-3.5 animate-spin" /> Wird gespeichert…
+          </span>
+        )}
+
+        {state === 'recording' ? (
+          <button
+            type="button"
+            onClick={() => void stop()}
+            title="Aufnahme beenden und speichern"
+            aria-label="Aufnahme beenden und speichern"
+            className="w-14 h-14 sm:w-10 sm:h-10 rounded-full bg-status-err text-on-accent flex items-center justify-center shadow-panel shrink-0"
+          >
+            <Square className="w-5 h-5 sm:w-4 sm:h-4 fill-current" />
+          </button>
+        ) : (
+          <button
+            type="button"
+            onClick={() => void start()}
+            disabled={state === 'uploading'}
+            title="Aufnahme starten"
+            aria-label="Aufnahme starten"
+            className="w-14 h-14 sm:w-10 sm:h-10 rounded-full bg-status-ok text-on-accent flex items-center justify-center shadow-panel shrink-0 disabled:opacity-40"
+          >
+            <Mic className="w-6 h-6 sm:w-5 sm:h-5" />
+          </button>
+        )}
+
+        {state === 'ready' && (
+          <button
+            type="button"
+            onClick={() => fileRef.current?.click()}
+            title="Audiodatei hochladen"
+            className="btn-secondary h-11 sm:h-8 px-3 text-xs flex items-center gap-1.5 shrink-0"
+          >
+            <Upload className="w-3.5 h-3.5" /> <span className="hidden sm:inline">Datei</span>
+          </button>
+        )}
+        <button
+          type="button"
+          onClick={cancel}
+          disabled={state === 'uploading'}
+          title="Abbrechen (Esc)"
+          className="w-11 h-11 sm:w-7 sm:h-7 flex items-center justify-center rounded-btn text-muted hover:text-main hover:bg-panel shrink-0 disabled:opacity-40"
+        >
+          <X className="w-4 h-4" />
+        </button>
+      </div>
+      {error && <p className="text-xs text-status-err">{error}</p>}
+      <input
+        ref={fileRef}
+        type="file"
+        accept="audio/*"
+        hidden
+        onChange={(e) => {
+          const f = e.target.files?.[0];
+          if (f) void upload(f, f.name || 'audio');
+        }}
+      />
+    </div>
+  );
+};