Fix display control review findings

[olujicz]

Summary

• Fix DDC hardware gating and fallback behavior across brightness control and the menu panel.
• Fix shortcut recorder focus and missed schedule event handling.
• Polish Hardware Control settings: disabled unavailable control modes, clearer DDC support status, and tighter advanced stepper layout.

Validation

• just format
• just lint
• just format-check
• git diff --check
• just test
• just build
• just build-appstore