feat: add WebVTT context generation to chat WebSocket endpoint

- Import topics_to_webvtt_named and recordings controller
- Add _get_is_multitrack helper function
- Generate WebVTT context on WebSocket connection
- Add get_context message type to retrieve WebVTT
- Maintain backward compatibility with echo for other messages
- Add test fixture and test for WebVTT context generation

Implements task fn-1.2: WebVTT context generation for transcript chat

.flow/specs/fn-1.4.md

@@ -0,0 +1,22 @@
+# Task 4: Register WebSocket Route
+
+**File:** `server/reflector/app.py` (modify)
+**Lines:** ~3
+**Dependencies:** Task 3
+
+## Objective
+Register chat router in FastAPI app.
+
+## Implementation
+```python
+# Add import
+from reflector.views.transcripts_chat import router as transcripts_chat_router
+
+# Add to route registration section
+app.include_router(transcripts_chat_router, prefix="/v1", tags=["transcripts"])
+```
+
+## Validation
+- [ ] Route appears in OpenAPI docs at `/docs`
+- [ ] WebSocket endpoint accessible from frontend
+- [ ] No import errors