feat: Auto-save voice recordings for model training

- Add /api/recordings endpoint with full CRUD operations
- Create voice_recordings SQLite table for metadata
- Save audio files to server/recordings/ as .webm
- Store transcription, duration, microphone name, file size
- Auto-save on each Whisper recording completion

frontend/src/components/FloatingVoice.vue

@@ -71,6 +71,7 @@ const showMicSelector = ref(false)
 const lastAudioUrl = ref<string>('')
 const isPlayingAudio = ref(false)
 let audioElement: HTMLAudioElement | null = null
+let recordingStartTime = 0
 
 function playLastAudio() {
   if (!lastAudioUrl.value) return
@@ -98,6 +99,42 @@ function saveAudioForPlayback(blob: Blob) {
     URL.revokeObjectURL(lastAudioUrl.value)
   }
   lastAudioUrl.value = URL.createObjectURL(blob)
+
+  // Also save to backend for training data
+  saveRecordingToBackend(blob)
+}
+
+async function saveRecordingToBackend(blob: Blob) {
+  try {
+    const duration_ms = Date.now() - recordingStartTime
+    const reader = new FileReader()
+
+    reader.onloadend = async () => {
+      const base64 = (reader.result as string).split(',')[1]
+
+      const response = await fetch(`http://${window.location.hostname}:4100/api/recordings`, {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({
+          audio: base64,
+          transcription: transcript.value.trim(),
+          microphone: currentMicName.value,
+          duration_ms
+        })
+      })
+
+      const data = await response.json()
+      if (data.success) {
+        console.log(`[Voice] Recording saved: ${data.filename} (${(data.size / 1024).toFixed(1)} KB)`)
+      } else {
+        console.error('[Voice] Failed to save recording:', data.error)
+      }
+    }
+
+    reader.readAsDataURL(blob)
+  } catch (e) {
+    console.error('[Voice] Error saving recording:', e)
+  }
 }
 
 const currentMicName = computed(() => {
@@ -438,6 +475,7 @@ async function startWhisperRecording() {
     // Start recording
     mediaRecorder.start(100) // Collect data every 100ms
     isRecording.value = true
+    recordingStartTime = Date.now()
 
     // Send chunks periodically for progressive transcription
     chunkInterval = window.setInterval(() => {