style: unify keyboard shortcut hints across tools using Pastel style

- Add shortcut hints below tool descriptions in Figlet and Units pages
- Revert experimental button-based shortcut layout in Units
- Remove redundant shortcut hints from Units footer
- Ensure consistent kbd tag styling across the application

app/(app)/units/page.tsx

@@ -9,6 +9,14 @@ export default function UnitsPage() {
           <p className="text-muted-foreground">
             Smart unit converter with 187 units across 23 categories
           </p>
+          <div className="mt-3 flex flex-wrap gap-2 text-xs text-muted-foreground">
+            <kbd className="px-2 py-1 bg-muted rounded border">/</kbd>
+            <span>Focus Search</span>
+            <kbd className="px-2 py-1 bg-muted rounded border ml-3">Ctrl+K</kbd>
+            <span>Command Palette</span>
+            <kbd className="px-2 py-1 bg-muted rounded border ml-3">ESC</kbd>
+            <span>Close Dialogs</span>
+          </div>
         </div>
         <MainConverter />
       </div>