Add skinnable LVGL analog clock

[bdbarnett]

What changed

• add a self-contained, responsive LVGL analog clock example
• include eight validated round, rectangular, and rounded-rectangle skins
• add a numbered, resolution-aware skin picker with immediate switching
• add glass shimmer, scalable typography, and external skin registration plumbing
• add a generated gallery thumbnail, card, and example package inventory entry

Why

This provides a realistic analog clock/watch example that demonstrates responsive LVGL styling and theme composition across 240–720 pixel displays.

Validation

• Ruff and Python compilation
• gallery generator check
• pre-commit manifest and gallery refresh hooks
• desktop LVGL runs at 240×240, 240×720, 720×240, and 720×720
• MicroPython browser harness rendering and interactive skin selection

[cursor]

Bugbot is not enabled for your account, so this pull request was not reviewed.

Enable Bugbot in the Cursor dashboard to get automatic reviews on future PRs.