feat: implement backend connection checks and add no_backend_required…

[robberwick]

This pull request introduces several changes to the blinkstick package, focusing on adding backend connection checks and improving the structure and functionality of the codebase. The most important changes include adding a new decorator to manage backend requirements, implementing a new exception for connection issues, and updating tests to reflect these changes.

Backend connection management:

• src/blinkstick/clients/blinkstick.py: Added a __getattribute__ method to ensure all callable attributes require a backend unless marked with the no_backend_required attribute.
• src/blinkstick/decorators.py: Introduced the no_backend_required decorator to mark methods that do not need a backend connection.

Exception handling:

• src/blinkstick/exceptions.py: Added a new NotConnected exception to handle cases where methods are called without a backend connection.

Testing updates:

• tests/clients/test_blinkstick.py: Updated tests to include checks for backend connection requirements and added a new test to ensure all methods require a backend.

Import reorganization:

• src/blinkstick/clients/blinkstick.py: Reorganized imports for better readability and maintainability.

[Copilot]

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