- Add calibration submenu with three options: Cancel (default), Calibrate, and Clear
- Cancel returns to main menu to prevent accidental calibration
- Calibrate runs system_setZeroAngle() and displays "Calibrated" confirmation
- Clear runs system_clearZeroAngle() and displays "Cleared" confirmation
- Use LVGL timer for non-blocking 1-second confirmation messages
- Center confirmation messages both horizontally and vertically
- Use larger font (montserrat_16) for better readability
- Remove "Back" button from volume control page
- Center volume control elements vertically on screen
- Improve overall menu navigation and visual consistency
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
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