- Add drawPixelGray to GfxRenderer for letterbox fill rendering
- Add PRERENDER_THUMB_HEIGHTS to UITheme for placeholder cover generation
- Add [env:mod] build environment to platformio.ini
- Implement sleep screen letterbox fill (solid/dithered) with edge
caching in SleepActivity, including placeholder cover fallback
- Add Clock settings category to SettingsActivity with timezone,
NTP sync, and set-time actions; replace CalibreSettings with
OpdsServerListActivity; add DynamicEnum rendering support
- Add long-press book management to RecentBooksActivity
Made-with: Cursor
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