Standardize API Responses Across All Controllers

[avirajsingh7]

Target issue : #66

This PR introduces a standardized API response format across all controllers using the APIResponse model.

Example For success response:

@router.post("/{user_id}", response_model=APIResponse[ProjectUserPublic])
def add_user(...):
    if not user:
        raise HTTPException(status_code=404, detail="User not found")

    try:
        new_project_user = add_user_to_project(session, project_id, user_id, is_admin)
        return APIResponse.success_response(new_project_user)
    except ValueError as e:
        raise HTTPException(status_code=400, detail=str(e))

How HTTP Exceptions Are Handled

With the introduction of a global exception handler, all HTTPException responses will be formatted uniformly.

What This Means:

• Developers can continue using raise HTTPException(status_code, "error message")
• The response format will always follow the standard structure
• Temporary "detail" field is retained for backward compatibility