Implement authentication and chat functionality with JWT support

- Added `auth.py` for mock login and JWT issuance.
- Introduced `chat.py` for handling chat requests with role-based access control.
- Enhanced `main.py` to include new routers and middleware for tracing.
- Implemented input validation in `input_guard.py` to prevent SQL injection.
- Created repositories for managing agent sessions and audit logs.
- Added exception handling for authorization errors.
- Updated settings to include JWT configuration.
- Introduced tests for authentication and input validation.

tests/test_wave0_trace.py

@@ -0,0 +1,13 @@
+"""Wave 0：trace_id 测试。"""
+
+
+def test_health_returns_trace_id(client):
+    resp = client.get("/health")
+    assert resp.status_code == 200
+    assert resp.headers.get("X-Trace-Id")
+    assert resp.json()["trace_id"]
+
+
+def test_trace_id_echo(client):
+    resp = client.get("/health", headers={"X-Trace-Id": "trace-fixed-001"})
+    assert resp.headers["X-Trace-Id"] == "trace-fixed-001"