Add iOS Safari support for voice commands with MediaRecorder fallback

Frontend changes:
- Add MediaRecorder fallback for iOS Safari (no Web Speech API support)
- Automatically detect browser capabilities and use appropriate method
- Add usesFallback flag to track which method is being used
- Update UI to show "Recording..." vs "Listening..." based on method
- Add iOS-specific indicator text
- Handle microphone permissions and errors properly

Backend changes:
- Update /api/v1/voice/transcribe to accept both audio files and text
- Support text-based classification (from Web Speech API)
- Support audio file transcription + classification (from MediaRecorder)
- Return unified response format with transcript and classification

How it works:
- Chrome/Edge: Uses Web Speech API for realtime transcription
- iOS Safari: Records audio with MediaRecorder, sends to server for transcription
- Fallback is transparent to the user with appropriate UI feedback

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

maternal-web/components/voice/VoiceInputButton.tsx

@@ -42,7 +42,7 @@ export function VoiceInputButton({
   const [isProcessing, setIsProcessing] = useState(false);
   const [classificationResult, setClassificationResult] = useState<any>(null);
 
-  const { isListening, isSupported, transcript, error, startListening, stopListening, reset } =
+  const { isListening, isSupported, transcript, error, usesFallback, startListening, stopListening, reset } =
     useVoiceInput();
 
   // Auto-classify when we get a final transcript
@@ -215,10 +215,18 @@ export function VoiceInputButton({
             {/* Status text */}
             <Typography variant="body1" color="text.secondary" gutterBottom>
               {isListening
-                ? 'Listening... Speak now'
+                ? usesFallback
+                  ? 'Recording... Speak now'
+                  : 'Listening... Speak now'
                 : 'Click the microphone to start'}
             </Typography>
 
+            {usesFallback && !isListening && !transcript && (
+              <Typography variant="caption" color="text.secondary" sx={{ mt: 1, display: 'block' }}>
+                Using audio recording mode (iOS Safari)
+              </Typography>
+            )}
+
             {/* Transcript */}
             {transcript && (
               <Box sx={{ mt: 3, p: 2, bgcolor: 'grey.100', borderRadius: 1 }}>