Summary

Fixes #126

On non-US keyboards (e.g. British, German, French), some keys produce different characters than on a US layout. The hotkey display was using a hardcoded lookup table that mapped physical key codes to US keyboard characters — so key code 10 (the ISO key between Escape and Tab) was missing entirely, and punctuation keys like [, ;, ' would show their US characters even on layouts where those keys produce ü, ö, ä, etc.

The broken fallback for unmapped keys converted the raw key code number to a Unicode character — key code 10 becomes U+000A (line feed), which is invisible. That's why the UI showed an empty box.

This PR replaces the hardcoded character table with a layout-aware lookup (UCKeyTranslate) that asks macOS what character each key actually produces on the user's current keyboard layout. The hardcoded table is kept only for keys with semantic names (Return, Tab, Space, Delete, Escape, arrow keys, modifiers) where the name is more useful than the character.

A US QWERTY fallback map is retained for edge cases where TIS layout data is unavailable (e.g. emoji or CJK input sources), so labels degrade gracefully rather than showing ? for every key.

Test plan

• On a British keyboard layout, assign § (or ⇧ + § for ±) as a hotkey — verify it renders correctly
• On a US keyboard layout, verify all existing hotkeys still display correctly
• Check hotkey display in: Settings, recording overlay, menu bar, and welcome screen
• Verify the hotkey still triggers correctly after reassignment
• If possible, test with a non-QWERTY layout (e.g. German QWERTZ) — punctuation keys should show their actual characters