feat: add login, session cookies, and get_current_user

backend/app/models/auth_session.py

@@ -0,0 +1,32 @@
+import hashlib
+import secrets
+import uuid
+from datetime import datetime, timedelta, timezone
+
+from sqlalchemy import DateTime, ForeignKey, String
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.db import Base
+
+SESSION_TTL = timedelta(days=14)
+
+
+class AuthSession(Base):
+    __tablename__ = "auth_sessions"
+
+    id: Mapped[uuid.UUID] = mapped_column(primary_key=True, default=uuid.uuid4)
+    user_id: Mapped[uuid.UUID] = mapped_column(ForeignKey("users.id"))
+    token_hash: Mapped[str] = mapped_column(String(64), unique=True, index=True)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), default=lambda: datetime.now(timezone.utc)
+    )
+    expires_at: Mapped[datetime] = mapped_column(DateTime(timezone=True))
+
+
+def generate_session_token() -> tuple[str, str]:
+    raw = secrets.token_urlsafe(32)
+    return raw, hash_token(raw)
+
+
+def hash_token(raw: str) -> str:
+    return hashlib.sha256(raw.encode()).hexdigest()