Replaced all inline error messages with the standardized `api_error` helper for consistent error response formatting. This improves clarity, maintainability, and ensures uniform error structures across the application. Updated logging for collector failures to include error class and switched to warning level for target unreachable scenarios.
Introduced a backend API endpoint for changing user passwords with validation. Added a new "User Settings" page in the frontend to allow users to update their passwords, including a matching UI update for navigation and styles.
