feat: enhance Arrs integration, NZBDav performance, and provider metrics

[drondeseries]

Summary

This PR introduces several key enhancements to improve Arrs integration reliability, importer performance, and system observability.

Key Changes

1. Stable Arrs ID Tracking (Sonarr/Radarr Matching)

• Implemented persistent GUID-based tracking (Download ID) from the initial 'Grab' through to 'History'.
• Updated the SABnzbd API compatibility layer to capture indexer GUIDs or generate fresh UUIDs.
• This resolves the long-standing issue where Sonarr/Radarr could not automatically match history items, eliminating the need for manual imports.

2. NZBDav Importer Enhancements

• Added support for compressed NZB blobs using zstd decompression.
• Implemented compatibility for the alpha version database schema used by newer NZBDav instances.
• Optimized blob parsing logic for better performance.

3. Per-Provider Performance Metrics

• Introduced persistent tracking of download volume for each configured NNTP provider.
• Added support for both cumulative total volume and rolling 24-hour volume per provider.
• Created a new table to maintain high-resolution history.

4. Dashboard UI Updates

• Enhanced the Provider Cards on the dashboard to display 'Total Downloaded' and 'Last 24h' stats.
• Improved real-time status visibility for multi-provider setups.

5. Database & CI

• Added migrations up to Version 21 to support the new tracking fields.
• Fixed migration boundary markers to ensure reliable automated schema updates.
• Resolved compilation and test schema issues identified during integration.