feat: integrate emoji-mart and refactor emoji usage

- Added @emoji-mart/data and @emoji-mart/react dependencies for enhanced emoji support.
- Replaced static emoji characters with Emoji component in various UI components for consistency and improved rendering.
- Updated generateDateTitle function to return an object with emoji and text for better structure.
- Marked the task for removing emojis from the UI as complete in TODO.md.

src/components/ui/header/HeaderDesktop.tsx

@@ -4,6 +4,7 @@ import { AuthButton } from '@/components/AuthButton';
 import { HeaderControls } from './HeaderControls';
 import { ThemeDropdown } from './ThemeDropdown';
 import { useKeyboardShortcutsModal } from '@/contexts/KeyboardShortcutsContext';
+import { Emoji } from '@/components/ui/Emoji';
 
 interface HeaderDesktopProps {
   title: string;
@@ -47,7 +48,7 @@ export function HeaderDesktop({ title, subtitle, syncing }: HeaderDesktopProps)
           className="text-[var(--muted-foreground)] hover:text-[var(--primary)] transition-colors p-1 rounded-md hover:bg-[var(--card-hover)]"
           title="Raccourcis clavier (Cmd+?)"
         >
-          ⌨️
+          <Emoji emoji="⌨️" size={16} />
         </button>
         <ThemeDropdown variant="desktop" />
         <AuthButton />