Phase 4: cloud backend — licensing, heartbeat, site management

- New cloud_backend/ FastAPI service on port 8001 (SQLite for dev, swappable to PostgreSQL)
- Endpoints: sysadmin auth (JWT), site registration, lock/unlock, heartbeat (X-Site-ID + X-Site-Key headers)
- Default sysadmin seeded on first startup from ADMIN_USERNAME/ADMIN_PASSWORD env vars
- cloud_backend added to docker-compose.yml with persistent data volume at ./data/cloud/
- local_backend cloud_sync.py updated to use correct /api/heartbeat/ endpoint with header auth
- local_backend config.py: added SITE_KEY setting
- Smoke tested: login, register site, heartbeat, lock, unlock, list all pass

cloud_backend/auth_utils.py

@@ -0,0 +1,44 @@
+from datetime import datetime, timedelta, timezone
+from jose import jwt, JWTError
+from passlib.context import CryptContext
+from fastapi import Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordBearer
+from sqlalchemy.orm import Session
+
+from config import settings
+from database import get_db
+from models.admin import Admin
+
+pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
+oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/api/auth/login")
+
+ALGORITHM = "HS256"
+
+
+def hash_password(password: str) -> str:
+    return pwd_context.hash(password)
+
+
+def verify_password(plain: str, hashed: str) -> bool:
+    return pwd_context.verify(plain, hashed)
+
+
+def create_access_token(data: dict) -> str:
+    payload = data.copy()
+    payload["exp"] = datetime.now(timezone.utc) + timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
+    return jwt.encode(payload, settings.SECRET_KEY, algorithm=ALGORITHM)
+
+
+def get_current_admin(token: str = Depends(oauth2_scheme), db: Session = Depends(get_db)) -> Admin:
+    try:
+        payload = jwt.decode(token, settings.SECRET_KEY, algorithms=[ALGORITHM])
+        username: str = payload.get("sub")
+        if not username:
+            raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid token")
+    except JWTError:
+        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid token")
+
+    admin = db.query(Admin).filter(Admin.username == username).first()
+    if not admin:
+        raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED, detail="Admin not found")
+    return admin