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/ui/Header.tsx

@@ -7,6 +7,7 @@ import Link from 'next/link';
 import { useState } from 'react';
 import { Theme } from '@/lib/theme-config';
 import { THEME_CONFIG, getThemeMetadata } from '@/lib/theme-config';
+import { useKeyboardShortcutsModal } from '@/contexts/KeyboardShortcutsContext';
 
 interface HeaderProps {
   title?: string;
@@ -20,6 +21,7 @@ export function Header({ title = "TowerControl", subtitle = "Task Management", s
   const pathname = usePathname();
   const [mobileMenuOpen, setMobileMenuOpen] = useState(false);
   const [themeDropdownOpen, setThemeDropdownOpen] = useState(false);
+  const { openModal: openShortcutsModal } = useKeyboardShortcutsModal();
 
   // Liste des thèmes disponibles avec leurs labels et icônes
   const themes: { value: Theme; label: string; icon: string }[] = THEME_CONFIG.allThemes.map(themeValue => {
@@ -97,6 +99,15 @@ export function Header({ title = "TowerControl", subtitle = "Task Management", s
 
             {/* Controls mobile/tablette */}
             <div className="flex items-center gap-2 flex-shrink-0">
+              {/* Keyboard Shortcuts */}
+              <button
+                onClick={openShortcutsModal}
+                className="text-[var(--muted-foreground)] hover:text-[var(--primary)] transition-colors p-2 rounded-md hover:bg-[var(--card-hover)]"
+                title="Raccourcis clavier (Cmd+?)"
+              >
+                ⌨️
+              </button>
+              
               {/* Theme Dropdown */}
               <div className="relative">
                 <button
@@ -197,6 +208,15 @@ export function Header({ title = "TowerControl", subtitle = "Task Management", s
                 </Link>
               ))}
               
+              {/* Keyboard Shortcuts desktop */}
+              <button
+                onClick={openShortcutsModal}
+                className="text-[var(--muted-foreground)] hover:text-[var(--primary)] transition-colors p-1 rounded-md hover:bg-[var(--card-hover)]"
+                title="Raccourcis clavier (Cmd+?)"
+              >
+                ⌨️
+              </button>
+              
               {/* Theme Dropdown desktop */}
               <div className="relative">
                 <button