feat(auth): authentication module with multi-tenant isolation (RFC-001)

Introduce an always-on auth layer with auto-created admin on first boot,
multi-tenant isolation for threads/stores, and a full setup/login flow.

Backend
- JWT access tokens with `ver` field for stale-token rejection; bump on
  password/email change
- Password hashing, HttpOnly+Secure cookies (Secure derived from request
  scheme at runtime)
- CSRF middleware covering both REST and LangGraph routes
- IP-based login rate limiting (5 attempts / 5-min lockout) with bounded
  dict growth and X-Forwarded-For bypass fix
- Multi-worker-safe admin auto-creation (single DB write, WAL once)
- needs_setup + token_version on User model; SQLite schema migration
- Thread/store isolation by owner; orphan thread migration on first admin
  registration
- thread_id validated as UUID to prevent log injection
- CLI tool to reset admin password
- Decorator-based authz module extracted from auth core

Frontend
- Login and setup pages with SSR guard for needs_setup flow
- Account settings page (change password / email)
- AuthProvider + route guards; skips redirect when no users registered
- i18n (en-US / zh-CN) for auth surfaces
- Typed auth API client; parseAuthError unwraps FastAPI detail envelope

Infra & tooling
- Unified `serve.sh` with gateway mode + auto dep install
- Public PyPI uv.toml pin for CI compatibility
- Regenerated uv.lock with public index

Tests
- HTTP vs HTTPS cookie security tests
- Auth middleware, rate limiter, CSRF, setup flow coverage

backend/tests/test_custom_agent.py

@@ -439,6 +439,15 @@ class TestAgentsAPI:
         assert "agent-one" in names
         assert "agent-two" in names
 
+    def test_list_agents_includes_soul(self, agent_client):
+        agent_client.post("/api/agents", json={"name": "soul-agent", "soul": "My soul content"})
+
+        response = agent_client.get("/api/agents")
+        assert response.status_code == 200
+        agents = response.json()["agents"]
+        soul_agent = next(a for a in agents if a["name"] == "soul-agent")
+        assert soul_agent["soul"] == "My soul content"
+
     def test_get_agent(self, agent_client):
         agent_client.post("/api/agents", json={"name": "test-agent", "soul": "Hello world"})