Implement caching for Proxmox API calls

[PAzter1101]

This PR implements caching to reduce the number of requests to the Proxmox API as requested in #2.

Changes Made

• Added VMCache class to handle VM information caching with TTL
• Implemented node caching with configurable TTL (default 60 seconds)
• Cache VM locations and status information
• Update cache entries when VM states change (start/stop)
• Reduce API calls in get_node_by_vmid and update_state methods
• Clear cache entries when VMs are deleted
• Added clear_caches method for manual cache invalidation

Implementation Details

• VM cache uses a dictionary with TTL for each entry
• Node cache uses a simple TTL-based approach
• Cache is updated automatically when VMs are created, deleted, started, or stopped
• Cache entries are invalidated automatically after TTL expires
• Fallback to API calls when cache misses or expires

Testing

The caching system has been tested with the following scenarios:

• VM creation and deletion
• VM start and stop operations
• Node queries
• Cache invalidation after TTL
• Cache updates on VM state changes

Fixes #2