Upgrade to Avalonia 12 and fix keyboard/fan control state handling

[RezaT4795]

Summary

This PR upgrades the GUI project to Avalonia 12 and fixes several state-handling issues in the Linux GUI.

The main focus is making the Keyboard Lighting and Power & Performance sections behave consistently across app relaunches, while also hardening daemon communication against rapid repeated UI actions.

Changes

Keyboard Lighting

• Fixed Zone Color Control resetting to the default blue/orange/green/yellow colors on every launch.
• Added GUI-side persistence for the user's last selected four-zone keyboard color preset.
• Fixed Static Mode applying the four Zone Color Control colors instead of the selected single effect color.
• Preserved the user's Zone Color Control colors when Static Mode is applied.
• Added separate GUI-side persistence for Lighting Effect settings.
• Fixed Static Mode color being reset after relaunch.
• Fixed Left-to-right / Right-to-left direction selection not being restored after relaunch.
• Explicitly sync both direction radio buttons instead of relying on one radio button to imply the other.

Power & Performance

• Fixed Max Fan Speed being restored as Manual mode with CPU/GPU set to 100% after relaunch.
• The GUI now distinguishes fan modes correctly:
  • 0 / 0 = Auto
  • 100 / 100 = Max
  • anything else = Manual

Daemon communication

• Fixed a crash that could happen when rapidly sending fan-speed commands.
• Serialized daemon socket commands so multiple JSON responses cannot be mixed together and parsed as one invalid JSON document.
• Added UI-side protection against rapid duplicate manual fan-speed submissions.
• Added safer exception handling so daemon communication errors do not crash the Avalonia UI.

Refactoring / cleanup

• Cleaned up the affected UI state synchronization code.
• Reduced duplicated preset read/write logic.
• Centralized keyboard color, direction, and preset handling helpers.
• Kept the existing behavior and project structure intact.

Testing

Tested manually on a PHN16-72 with Linux/Slackware-current.

Verified:

• Custom four-zone keyboard colors persist across DAMX-GUI relaunches.
• Static Mode applies one selected color correctly.
• Static Mode no longer overwrites the saved Zone Color Control preset.
• Static Mode color persists across relaunches.
• Lighting direction selection persists across relaunches.
• Max Fan Speed is restored as Max after relaunch, not Manual.
• Rapid manual fan-speed changes no longer crash the GUI.