Complete backend infrastructure and authentication system

Co-authored-by: mblanke <9078342+mblanke@users.noreply.github.com>

backend/app/core/deps.py

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+from typing import List, Optional
+from fastapi import Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordBearer
+from sqlalchemy.orm import Session
+
+from app.core.database import get_db
+from app.core.security import verify_token
+from app.models.user import User
+
+# OAuth2 scheme for token extraction
+oauth2_scheme = OAuth2PasswordBearer(tokenUrl="/api/auth/login")
+
+
+async def get_current_user(
+    token: str = Depends(oauth2_scheme),
+    db: Session = Depends(get_db)
+) -> User:
+    """
+    Extract and validate JWT from Authorization header
+    
+    Args:
+        token: JWT token from Authorization header
+        db: Database session
+    
+    Returns:
+        Current user object
+    
+    Raises:
+        HTTPException: If token is invalid or user not found
+    """
+    credentials_exception = HTTPException(
+        status_code=status.HTTP_401_UNAUTHORIZED,
+        detail="Could not validate credentials",
+        headers={"WWW-Authenticate": "Bearer"},
+    )
+    
+    # Verify and decode token
+    payload = verify_token(token)
+    if payload is None:
+        raise credentials_exception
+    
+    user_id: Optional[int] = payload.get("sub")
+    if user_id is None:
+        raise credentials_exception
+    
+    # Get user from database
+    user = db.query(User).filter(User.id == user_id).first()
+    if user is None:
+        raise credentials_exception
+    
+    return user
+
+
+async def get_current_active_user(
+    current_user: User = Depends(get_current_user)
+) -> User:
+    """
+    Ensure user is active
+    
+    Args:
+        current_user: Current user from get_current_user
+    
+    Returns:
+        Active user object
+    
+    Raises:
+        HTTPException: If user is inactive
+    """
+    if not current_user.is_active:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Inactive user"
+        )
+    return current_user
+
+
+def require_role(allowed_roles: List[str]):
+    """
+    Role-based access control dependency factory
+    
+    Args:
+        allowed_roles: List of roles that are allowed to access the endpoint
+    
+    Returns:
+        Dependency function that checks user role
+    """
+    async def role_checker(current_user: User = Depends(get_current_active_user)) -> User:
+        if current_user.role not in allowed_roles:
+            raise HTTPException(
+                status_code=status.HTTP_403_FORBIDDEN,
+                detail="Insufficient permissions"
+            )
+        return current_user
+    
+    return role_checker
+
+
+async def get_tenant_id(current_user: User = Depends(get_current_active_user)) -> int:
+    """
+    Extract tenant_id from current user for scoping queries
+    
+    Args:
+        current_user: Current active user
+    
+    Returns:
+        Tenant ID
+    """
+    return current_user.tenant_id