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/app/gateway/deps.py

@@ -3,38 +3,22 @@
 **Getters** (used by routers): raise 503 when a required dependency is
 missing, except ``get_store`` which returns ``None``.
 
-Initialization is handled directly in ``app.py`` via :class:`AsyncExitStack`.
+Initialization is handled directly in ``app.py`` via :class:`AsyncExitStack``.
 """
 
 from __future__ import annotations
 
 from collections.abc import AsyncGenerator
 from contextlib import AsyncExitStack, asynccontextmanager
+from typing import TYPE_CHECKING
 
 from fastapi import FastAPI, HTTPException, Request
 
 from deerflow.runtime import RunManager, StreamBridge
 
-
-@asynccontextmanager
-async def langgraph_runtime(app: FastAPI) -> AsyncGenerator[None, None]:
-    """Bootstrap and tear down all LangGraph runtime singletons.
-
-    Usage in ``app.py``::
-
-        async with langgraph_runtime(app):
-            yield
-    """
-    from deerflow.agents.checkpointer.async_provider import make_checkpointer
-    from deerflow.runtime import make_store, make_stream_bridge
-
-    async with AsyncExitStack() as stack:
-        app.state.stream_bridge = await stack.enter_async_context(make_stream_bridge())
-        app.state.checkpointer = await stack.enter_async_context(make_checkpointer())
-        app.state.store = await stack.enter_async_context(make_store())
-        app.state.run_manager = RunManager()
-        yield
-
+if TYPE_CHECKING:
+    from app.gateway.auth.local_provider import LocalAuthProvider
+    from app.gateway.auth.repositories.sqlite import SQLiteUserRepository
 
 # ---------------------------------------------------------------------------
 # Getters – called by routers per-request
@@ -68,3 +52,102 @@ def get_checkpointer(request: Request):
 def get_store(request: Request):
     """Return the global store (may be ``None`` if not configured)."""
     return getattr(request.app.state, "store", None)
+
+
+# ---------------------------------------------------------------------------
+# Auth helpers (used by authz.py)
+# ---------------------------------------------------------------------------
+
+# Cached singletons to avoid repeated instantiation per request
+_cached_local_provider: LocalAuthProvider | None = None
+_cached_repo: SQLiteUserRepository | None = None
+
+
+def get_local_provider() -> LocalAuthProvider:
+    """Get or create the cached LocalAuthProvider singleton."""
+    global _cached_local_provider, _cached_repo
+    if _cached_repo is None:
+        from app.gateway.auth.repositories.sqlite import SQLiteUserRepository
+
+        _cached_repo = SQLiteUserRepository()
+    if _cached_local_provider is None:
+        from app.gateway.auth.local_provider import LocalAuthProvider
+
+        _cached_local_provider = LocalAuthProvider(repository=_cached_repo)
+    return _cached_local_provider
+
+
+async def get_current_user_from_request(request: Request):
+    """Get the current authenticated user from the request cookie.
+
+    Raises HTTPException 401 if not authenticated.
+    """
+    from app.gateway.auth import decode_token
+    from app.gateway.auth.errors import AuthErrorCode, AuthErrorResponse, TokenError, token_error_to_code
+
+    access_token = request.cookies.get("access_token")
+    if not access_token:
+        raise HTTPException(
+            status_code=401,
+            detail=AuthErrorResponse(code=AuthErrorCode.NOT_AUTHENTICATED, message="Not authenticated").model_dump(),
+        )
+
+    payload = decode_token(access_token)
+    if isinstance(payload, TokenError):
+        raise HTTPException(
+            status_code=401,
+            detail=AuthErrorResponse(code=token_error_to_code(payload), message=f"Token error: {payload.value}").model_dump(),
+        )
+
+    provider = get_local_provider()
+    user = await provider.get_user(payload.sub)
+    if user is None:
+        raise HTTPException(
+            status_code=401,
+            detail=AuthErrorResponse(code=AuthErrorCode.USER_NOT_FOUND, message="User not found").model_dump(),
+        )
+
+    # Token version mismatch → password was changed, token is stale
+    if user.token_version != payload.ver:
+        raise HTTPException(
+            status_code=401,
+            detail=AuthErrorResponse(code=AuthErrorCode.TOKEN_INVALID, message="Token revoked (password changed)").model_dump(),
+        )
+
+    return user
+
+
+async def get_optional_user_from_request(request: Request):
+    """Get optional authenticated user from request.
+
+    Returns None if not authenticated.
+    """
+    try:
+        return await get_current_user_from_request(request)
+    except HTTPException:
+        return None
+
+
+# ---------------------------------------------------------------------------
+# Runtime bootstrap
+# ---------------------------------------------------------------------------
+
+
+@asynccontextmanager
+async def langgraph_runtime(app: FastAPI) -> AsyncGenerator[None, None]:
+    """Bootstrap and tear down all LangGraph runtime singletons.
+
+    Usage in ``app.py``::
+
+        async with langgraph_runtime(app):
+            yield
+    """
+    from deerflow.agents.checkpointer.async_provider import make_checkpointer
+    from deerflow.runtime import make_store, make_stream_bridge
+
+    async with AsyncExitStack() as stack:
+        app.state.stream_bridge = await stack.enter_async_context(make_stream_bridge())
+        app.state.checkpointer = await stack.enter_async_context(make_checkpointer())
+        app.state.store = await stack.enter_async_context(make_store())
+        app.state.run_manager = RunManager()
+        yield