Shortcuts: Update modifier for macOS

Overview & Context

Update the macOS toggle modifier in the existing hotkey system from Cmd + Shift to Ctrl + Cmd. Windows/Linux bindings (Ctrl + Shift + <Key>) and P2T keys (Space, W) stay unchanged.

Technical Design & Interfaces

Affected files

• eventBindings.ts — modifier per OS.
• listener.ts — verify two-modifier matching with Control + Meta.
• useHotkeyCombination.tsx — uppercase the trailing key letter.
• hotkeys.test.ts — update modifier expectations.

Modifier matrix

Function	Windows / Linux	macOS
Microphone (toggle)	Ctrl + Shift + M	Ctrl + Cmd + M
Video (toggle)	Ctrl + Shift + V	Ctrl + Cmd + V
Fullscreen (toggle)	Ctrl + Shift + F	Ctrl + Cmd + F
Screen Share (toggle)	Ctrl + Shift + S	Ctrl + Cmd + S
Raise Hand (toggle)	Ctrl + Shift + H	Ctrl + Cmd + H
Microphone PTT (hold)	Space	Space
Whisper PTT (hold)	W	W

In code: modifier: isMacOS ? ['Control', 'Meta'] : ['Control', 'Shift'].

Implementation Tasks

• Replace Meta + Shift with Control + Meta for all five toggle bindings on macOS in eventBindings.ts
• Update useHotkeyCombination.tsx to uppercase the key letter
• Extend hotkeys.test.ts to assert Control + Meta matching on macOS
• Manual verification on macOS (Chrome, Firefox, Safari): all five toggles fire on Ctrl + Cmd + <Key> - Cmd + Shift + <Key> no longer triggers anything

Definition of Done (DoD)

• Manual verification successful on macOS (Chrome and Firefox) and one Windows/Linux browser to confirm no regression.
• Shortcut strings in tooltips and overlay show the key letter in uppercase
• Unit tests added/updated