feat: MVP-5 Sprint 2 - Command Palette and Global Shortcuts

- Add Command Palette (Ctrl+K / Cmd+K) with search and navigation
- Add global keyboard shortcuts: g h (dashboard), g n (notes), n (new note)
- Add keyboard shortcuts help dialog (?)
- Add shortcuts provider component
- Shortcuts ignore inputs/textareas for proper UX

src/app/layout.tsx

@@ -2,6 +2,8 @@ import type { Metadata } from 'next'
 import './globals.css'
 import { Toaster } from '@/components/ui/sonner'
 import { Header } from '@/components/header'
+import { CommandPalette } from '@/components/command-palette'
+import { ShortcutsProvider } from '@/components/shortcuts-provider'
 
 export const metadata: Metadata = {
   title: 'Recall - Gestor de Conocimiento Personal',
@@ -19,6 +21,8 @@ export default function RootLayout({
         <Header />
         {children}
         <Toaster />
+        <CommandPalette />
+        <ShortcutsProvider />
       </body>
     </html>
   )