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-1.1.md

@@ -0,0 +1,52 @@
+# Task 1: WebSocket Endpoint Skeleton
+
+**File:** `server/reflector/views/transcripts_chat.py`
+**Lines:** ~30
+**Dependencies:** None
+
+## Objective
+Create basic WebSocket endpoint with auth and connection handling.
+
+## Implementation
+```python
+from typing import Optional
+from fastapi import APIRouter, Depends, WebSocket, WebSocketDisconnect
+import reflector.auth as auth
+from reflector.db.transcripts import transcripts_controller
+
+router = APIRouter()
+
+@router.websocket("/transcripts/{transcript_id}/chat")
+async def transcript_chat_websocket(
+    transcript_id: str,
+    websocket: WebSocket,
+    user: Optional[auth.UserInfo] = Depends(auth.current_user_optional),
+):
+    # 1. Auth check
+    user_id = user["sub"] if user else None
+    transcript = await transcripts_controller.get_by_id_for_http(
+        transcript_id, user_id
+    )
+
+    # 2. Accept connection
+    await websocket.accept()
+
+    try:
+        # 3. Basic message loop (stub)
+        while True:
+            data = await websocket.receive_json()
+            await websocket.send_json({"type": "echo", "data": data})
+    except WebSocketDisconnect:
+        pass
+```
+
+## Validation
+- [ ] Endpoint accessible at `ws://localhost:1250/v1/transcripts/{id}/chat`
+- [ ] Auth check executes (404 if transcript not found)
+- [ ] Connection accepts
+- [ ] Echo messages back to client
+- [ ] Disconnect handled gracefully
+
+## Notes
+- Test with `websocat` or browser WebSocket client
+- Don't add LLM yet, just echo