feat: add login, session cookies, and get_current_user

backend/app/deps.py

@@ -0,0 +1,30 @@
+from datetime import datetime, timezone
+
+from fastapi import Cookie, Depends, HTTPException, status
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.db import get_db
+from app.models.auth_session import AuthSession, hash_token
+from app.models.user import User
+
+SESSION_COOKIE_NAME = "qm_session"
+
+
+async def get_current_user(
+    qm_session: str | None = Cookie(default=None),
+    db: AsyncSession = Depends(get_db),
+) -> User:
+    if qm_session is None:
+        raise HTTPException(status.HTTP_401_UNAUTHORIZED, "not authenticated")
+
+    token_hash = hash_token(qm_session)
+    result = await db.execute(select(AuthSession).where(AuthSession.token_hash == token_hash))
+    session = result.scalar_one_or_none()
+    if session is None or session.expires_at < datetime.now(timezone.utc):
+        raise HTTPException(status.HTTP_401_UNAUTHORIZED, "session expired")
+
+    user = await db.get(User, session.user_id)
+    if user is None:
+        raise HTTPException(status.HTTP_401_UNAUTHORIZED, "user not found")
+    return user