refactor: fix architectural issues across frontend and backend

Address all architecture review findings:

P0 fixes:
- Add API key authentication for admin endpoints (analytics, replay, openapi)
  and WebSocket connections via ADMIN_API_KEY env var
- Add PostgreSQL-backed PgSessionManager and PgInterruptManager for
  multi-worker production deployments (in-memory defaults preserved)

P1 fixes:
- Implement actual tool generation in OpenAPI approve_job endpoint
  using generate_tool_code() and generate_agent_yaml()
- Add missing clarification, interrupt_expired, and tool_result message
  handlers in frontend ChatPage

P2 fixes:
- Replace monkey-patching on CompiledStateGraph with typed GraphContext
- Replace 9-param dispatch_message with WebSocketContext dataclass
- Extract duplicate _envelope() into shared app/api_utils.py
- Replace mutable module-level counter with crypto.randomUUID()
- Remove hardcoded mock data from ReviewPage, use api.ts wrappers
- Remove `as any` type escape from ReplayPage

All 516 tests passing, 0 TypeScript errors.

backend/app/config.py

@@ -32,6 +32,8 @@ class Settings(BaseSettings):
 
     template_name: str = ""
 
+    admin_api_key: str = ""
+
     anthropic_api_key: str = ""
     openai_api_key: str = ""
     azure_openai_api_key: str = ""