feat: Step 7 & 9 - AI Chat + Voice client integration

Implement AI-powered chat interface with voice input capabilities.

Step 7 (Chat Interface):
- Create ChatInterface component with Vercel AI SDK useChat hook
- Create /api/chat route using Google Gemini (gemini-1.5-flash)
- Implement thoughtful interviewer system prompt
- Add real-time message streaming
- Auto-scroll to latest messages

Step 9 (Voice Client):
- Create MicrophoneRecorder component
- Integrate real-time voice transcription via Deepgram
- Direct WebSocket connection using temporary tokens
- Real-time transcript display in chat input
- Auto-submit on speech_final event
- Add @tabler/icons-react for microphone icons

Architecture:
- Client requests temporary Deepgram token from /api/voice-token
- MediaRecorder captures audio in 250ms chunks
- WebSocket sends audio directly to Deepgram
- Transcripts update chat input in real-time
- Final transcript auto-submits to AI chat

Security:
- Deepgram API key never exposed to client
- Temporary tokens expire in 60 seconds
- Chat requires authentication via SurrealDB JWT

Testing:
- Add magnitude test for voice recording flow
- Tests cover happy path with mocked WebSocket

Known Issue:
- Page compilation needs debugging (useChat import path verified)

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

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

pnpm-lock.yaml

@@ -38,6 +38,9 @@ importers:
       '@react-three/fiber':
         specifier: latest
         version: 9.4.0(@types/react@19.2.2)(react-dom@19.2.0(react@19.2.0))(react@19.2.0)(three@0.181.0)
+      '@tabler/icons-react':
+        specifier: ^3.35.0
+        version: 3.35.0(react@19.2.0)
       ai:
         specifier: latest
         version: 5.0.89(zod@4.1.12)
@@ -969,6 +972,14 @@ packages:
   '@swc/helpers@0.5.15':
     resolution: {integrity: sha512-JQ5TuMi45Owi4/BIMAJBoSQoOJu12oOk/gADqlcUL9JEdHB8vyjUSsxqeNXnmXHjYKMi2WcYtezGEEhqUI/E2g==}
 
+  '@tabler/icons-react@3.35.0':
+    resolution: {integrity: sha512-XG7t2DYf3DyHT5jxFNp5xyLVbL4hMJYJhiSdHADzAjLRYfL7AnjlRfiHDHeXxkb2N103rEIvTsBRazxXtAUz2g==}
+    peerDependencies:
+      react: '>= 16'
+
+  '@tabler/icons@3.35.0':
+    resolution: {integrity: sha512-yYXe+gJ56xlZFiXwV9zVoe3FWCGuZ/D7/G4ZIlDtGxSx5CGQK110wrnT29gUj52kEZoxqF7oURTk97GQxELOFQ==}
+
   '@tweenjs/tween.js@23.1.3':
     resolution: {integrity: sha512-vJmvvwFxYuGnF2axRtPYocag6Clbb5YS7kLL+SO/TeVFzHqDIWrNKYtcsPMibjDx9O+bu+psAy9NKfWklassUA==}
 
@@ -4103,6 +4114,13 @@ snapshots:
     dependencies:
       tslib: 2.8.1
 
+  '@tabler/icons-react@3.35.0(react@19.2.0)':
+    dependencies:
+      '@tabler/icons': 3.35.0
+      react: 19.2.0
+
+  '@tabler/icons@3.35.0': {}
+
   '@tweenjs/tween.js@23.1.3': {}
 
   '@tybys/wasm-util@0.10.1':