Test server socket runtime control

[rmens]

Description

The refactor in PR #77 introduced server socket runtime control as the primary method for managing silence detection and source forcing. This needs thorough testing before relying on it in production.

Test plan

Socket connectivity

• Verify socket file appears at /opt/liquidsoap/socket/liquidsoap.sock on the host
• Verify socat - UNIX-CONNECT:/opt/liquidsoap/socket/liquidsoap.sock connects successfully
• Verify socket survives container restart

Silence detection commands

• silence.status returns enabled on fresh start
• silence.disable disables silence detection
• silence.status returns disabled after disable
• silence.enable re-enables silence detection
• Verify silence detection actually stops triggering fallback when disabled
• Verify silence detection resumes triggering fallback when re-enabled

Source forcing commands

• radio_prod.status returns current mode and active source
• radio_prod.force studio_a forces Studio A
• radio_prod.force studio_b forces Studio B
• radio_prod.force fallback forces emergency fallback
• radio_prod.force invalid returns error message
• radio_prod.auto returns to automatic fallback mode
• radio_prod.skip skips to next available source
• Verify forced source persists until radio_prod.auto is called

Edge cases

• Verify state resets to defaults on container restart (silence detection enabled, auto mode)
• Test socket commands while no studio inputs are connected
• Test forcing a source that is not currently connected