Add WebSocket support for TrueNAS JSON-RPC 2.0 API

[jaycollett]

Summary

TrueNAS is deprecating the REST API (api/v2.0/) in version 26.04, requiring migration to JSON-RPC 2.0 over WebSocket. This PR adds the core WebSocket infrastructure needed to support TrueNAS CORE and SCALE apps.

Changes

• Add phrity/websocket dependency for WebSocket communication
• Add TrueNASWebSocketClient helper class that handles:
  • Connection to ws(s)://host/api/current
  • Authentication via auth.login_with_api_key
  • JSON-RPC 2.0 request/response formatting
  • TLS verification toggle
  • Proper connection cleanup

Technical Details

The WebSocket client uses the phrity/websocket v3.x library with proper SSL context configuration:

• Forces ALPN to HTTP/1.1 for WebSocket upgrade compatibility (TrueNAS nginx defaults to HTTP/2)
• Supports self-signed certificates when TLS verification is disabled

Companion PR

Depends on: linuxserver/Heimdall-Apps#889

This PR provides the core infrastructure. The TrueNAS app updates are in:

• Migrate TrueNAS apps to JSON-RPC 2.0 WebSocket API Heimdall-Apps#889 - Migrate TrueNAS apps to JSON-RPC 2.0 WebSocket API

Both PRs need to be merged for full functionality. Existing TrueNAS apps will continue to work with REST API until the companion PR is merged.

References

• Closes truenas app still use the deprecated REST API #1530
• TrueNAS JSON-RPC API Documentation

Backward Compatibility

TrueNAS Version	REST API	WebSocket	Notes
< 25.04	✅	❌	REST only
25.04	⚠️ Deprecated	✅	Both available
26.04+	❌ Removed	✅	WebSocket required

Test Plan

• Tested WebSocket connection with TrueNAS SCALE 25.10.1
• Verified authentication with API key
• Confirmed JSON-RPC 2.0 calls work (core.ping, system.info, alert.list)
• Tested with self-signed certificates (ignore_tls option)