feat: update website name retrieval and configuration handling

- Changed the retrieval of the website name in the sidebar component to use the `DbConfig` model for dynamic configuration.
- Updated the `set` method in the `DbConfig` model to allow null values for configuration.
- Refactored the public layout to use the website name from `DbConfig` instead of a hardcoded value.
- Adjusted the default value for maintenance mode and website name in the settings view to match the new configuration method.
- Modified the middleware to check the maintenance mode from the `DbConfig` model.
- Updated the `SettingsController` to use `has` instead of `filled` for checking request inputs related to maintenance mode and website name.