Adds snapshot creation and recovery support for linked and full VMs

[aschumann-virtualcable]

This pull request introduces improvements and fixes across the Proxmox service implementation and its test suite. The most significant changes include enhancements to snapshot management, stricter validation for clone types, improved test fixture consistency, and modernization of type annotations.

Enhancements to Proxmox service functionality:

• Added snapshot_creation and snapshot_recovery methods to ProxmoxService for automatic snapshot management, including background snapshot creation and recovery for linked user services.
• Improved validation logic in initialize to correctly check storage support for linked clones and raise errors when unsupported clone types are requested.

Test suite improvements and fixture consistency:

• Updated test fixtures and test cases to ensure consistent use of provider and service instances, improving reliability and accuracy of tests by explicitly passing provider instances. [1] [2] [3] [4] [5]
• Fixed test fixture creation to use the correct UUID and storage values, and modernized generator and mapping type annotations for better compatibility and clarity. [1] [2] [3] [4] [5]

Modernization and code cleanup:

• Refactored type annotations in both service and test code to use Python 3.9+ syntax (e.g., list[...], dict[...], str | None) and replaced typing with collections.abc where appropriate. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]

Exception handling improvements:

• Added new exception classes and improved exception handling in snapshot-related operations to provide clearer error logging and handling for missing snapshots and VM restoration failures. [1] [2]

Logging improvements:

• Enhanced logging in VM cloning to provide clearer parameter output and better debugging information.

These changes collectively improve the robustness, maintainability, and clarity of the Proxmox service codebase and its associated tests.