API key come hash SHA-256, una per sessione, TTL rinnovabile (#41)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/backend/models/orm/api_key.py

@@ -0,0 +1,25 @@
+"""API key sessions: one row per login, stored as a SHA-256 hash."""
+from datetime import datetime
+from typing import Optional
+
+from sqlalchemy import DateTime, ForeignKey, Integer, String
+from sqlalchemy.orm import Mapped, mapped_column
+
+from src.backend.database import Base
+
+
+class ApiKey(Base):
+    """One API key per login session.
+
+    Only the SHA-256 hex digest is stored, never the key. Dates are naive UTC.
+    """
+    __tablename__ = "api_keys"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
+    user_id: Mapped[int] = mapped_column(
+        Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
+    )
+    key_hash: Mapped[str] = mapped_column(String(64), nullable=False, unique=True, index=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime, nullable=False)
+    expires_at: Mapped[datetime] = mapped_column(DateTime, nullable=False)
+    last_used_at: Mapped[Optional[datetime]] = mapped_column(DateTime, nullable=True)