fix(gat562): show white breathing light instead of colorful marquee on NeoPixel standby

[ssp97]

Problem

Users with GAT562 Mesh Tracker Pro reported that after updating firmware, the NeoPixel 'breathing light' shows colorful colors during standby (showNotificationMarquee HSV cycling), while they preferred the previous standby behavior of a white light.

Change

In src/AmbientLightingThread.h:

• For GAT562 devices with HAS_NEOPIXEL, after the boot animation marquee finishes, transition to a white breathing effect instead of turning the LED off.
  • Color: RGB(255, 255, 255)
  • Max brightness: 30 (soft)
  • Breath period: 2 seconds
• Added _lastMarqueeCall tracking so the breathing effect pauses briefly when ExternalNotificationModule is actively showing notification marquees, avoiding LED flicker.
• Non-GAT562 NeoPixel devices keep the original behavior: LED turns off after boot.

Verification

• pio run -e gat562_mesh_tracker_pro ✅
• pio run -e gat562_mesh_tracker_pro_zhcn ✅