New config options:
- mode = "window" (rolling hours, default) or "today" (daily reset)
- start_time = "06:00" (when today mode resets)
- hold_overnight = true (keep overnight collage until first bird)
In "today" mode the collage only shows birds since start_time,
growing through the day. With hold_overnight=true, the display
keeps the previous full collage until the first bird is detected
after start_time (no blank screen at dawn).
Co-Authored-By: Claude Opus 4 <noreply@anthropic.com>
Chris Sader