feat(speech): add frontend speech API client and useSpeech hook

Adds transcribeAudio() and fetchSpeechHealth() to the API client,
and the useSpeech React hook for managing mic recording lifecycle.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/api/client.ts

@@ -20,3 +20,33 @@ export async function fetchServerInfo(): Promise<ServerInfo> {
   if (!res.ok) throw new Error(`Failed to fetch server info: ${res.status}`);
   return res.json();
 }
+
+export interface TranscriptionResult {
+  text: string;
+  language: string | null;
+  confidence: number | null;
+  duration_seconds: number;
+}
+
+export interface SpeechHealth {
+  available: boolean;
+  backend?: string;
+  reason?: string;
+}
+
+export async function transcribeAudio(audioBlob: Blob, filename = 'recording.webm'): Promise<TranscriptionResult> {
+  const formData = new FormData();
+  formData.append('file', audioBlob, filename);
+  const res = await fetch(`${BASE}/v1/speech/transcribe`, {
+    method: 'POST',
+    body: formData,
+  });
+  if (!res.ok) throw new Error(`Transcription failed: ${res.status}`);
+  return res.json();
+}
+
+export async function fetchSpeechHealth(): Promise<SpeechHealth> {
+  const res = await fetch(`${BASE}/v1/speech/health`);
+  if (!res.ok) return { available: false };
+  return res.json();
+}

frontend/src/hooks/useSpeech.ts

@@ -0,0 +1,92 @@
+import { useState, useCallback, useRef, useEffect } from 'react';
+import { transcribeAudio, fetchSpeechHealth } from '../api/client';
+
+export type SpeechState = 'idle' | 'recording' | 'transcribing';
+
+export function useSpeech() {
+  const [state, setState] = useState<SpeechState>('idle');
+  const [error, setError] = useState<string | null>(null);
+  const [available, setAvailable] = useState(false);
+  const mediaRecorderRef = useRef<MediaRecorder | null>(null);
+  const chunksRef = useRef<Blob[]>([]);
+  const streamRef = useRef<MediaStream | null>(null);
+
+  // Check if speech backend is available on mount
+  useEffect(() => {
+    fetchSpeechHealth()
+      .then((health) => setAvailable(health.available))
+      .catch(() => setAvailable(false));
+  }, []);
+
+  const startRecording = useCallback(async (): Promise<void> => {
+    setError(null);
+
+    if (!navigator.mediaDevices?.getUserMedia) {
+      setError('Microphone not supported in this browser');
+      return;
+    }
+
+    try {
+      const stream = await navigator.mediaDevices.getUserMedia({ audio: true });
+      streamRef.current = stream;
+
+      const recorder = new MediaRecorder(stream);
+      chunksRef.current = [];
+
+      recorder.ondataavailable = (e) => {
+        if (e.data.size > 0) chunksRef.current.push(e.data);
+      };
+
+      recorder.start();
+      mediaRecorderRef.current = recorder;
+      setState('recording');
+    } catch (err) {
+      setError('Microphone access denied');
+      setState('idle');
+    }
+  }, []);
+
+  const stopRecording = useCallback(async (): Promise<string> => {
+    return new Promise((resolve, reject) => {
+      const recorder = mediaRecorderRef.current;
+      if (!recorder || recorder.state !== 'recording') {
+        reject(new Error('Not recording'));
+        return;
+      }
+
+      recorder.onstop = async () => {
+        setState('transcribing');
+
+        // Stop all audio tracks
+        streamRef.current?.getTracks().forEach((track) => track.stop());
+        streamRef.current = null;
+
+        const blob = new Blob(chunksRef.current, { type: recorder.mimeType || 'audio/webm' });
+        chunksRef.current = [];
+
+        try {
+          const result = await transcribeAudio(blob);
+          setState('idle');
+          resolve(result.text);
+        } catch (err) {
+          setState('idle');
+          const msg = err instanceof Error ? err.message : 'Transcription failed';
+          setError(msg);
+          reject(err);
+        }
+      };
+
+      recorder.stop();
+    });
+  }, []);
+
+  return {
+    state,
+    error,
+    available,
+    startRecording,
+    stopRecording,
+    isRecording: state === 'recording',
+    isTranscribing: state === 'transcribing',
+  };
+}