feat: integrate global keyboard shortcuts across multiple components

- Added `KeyboardShortcutsProvider` to `RootLayout` for centralized keyboard shortcut management.
- Implemented `useGlobalKeyboardShortcuts` in `DailyPageClient`, `KanbanPageClient`, and `HomePageClient` to enhance navigation and task management with keyboard shortcuts.
- Updated `KeyboardShortcuts` component to render a modal for displaying available shortcuts, improving user accessibility.
- Enhanced `Header` component with buttons to open the keyboard shortcuts modal, streamlining user interaction.

src/components/KeyboardShortcuts.tsx

@@ -1,8 +1,19 @@
 'use client';
 
 import { useKeyboardShortcuts } from '@/hooks/useKeyboardShortcuts';
+import { useKeyboardShortcutsModal } from '@/contexts/KeyboardShortcutsContext';
+import { KeyboardShortcutsModal } from '@/components/ui/KeyboardShortcutsModal';
 
 export function KeyboardShortcuts() {
   useKeyboardShortcuts();
-  return null; // Ce composant ne rend rien, il gère juste les raccourcis
+  const { isOpen, shortcuts, closeModal } = useKeyboardShortcutsModal();
+  
+  return (
+    <KeyboardShortcutsModal
+      isOpen={isOpen}
+      onClose={closeModal}
+      shortcuts={shortcuts}
+      title="Raccourcis clavier"
+    />
+  );
 }