feat: implement responsive design enhancements

- Add touch-optimized tap targets (44x44px minimum for iOS)
- Enhance mobile responsiveness across all components
- Improve button sizing and spacing for touch interactions
- Add responsive text sizing and layout adjustments
- Implement mobile-first modal behavior (bottom sheet on mobile)
- Enhance form controls with better touch targets
- Add active states for better touch feedback
- Improve grid layouts for various screen sizes
- Add smooth scrolling and better focus states
- Optimize FilterPanel for mobile with grid layouts
- Enhance all interactive elements with tap-target classes

Requirements: 7.1, 7.2

app/list/[id]/item/[itemId]/edit/page.tsx

@@ -19,21 +19,21 @@ export default async function EditItemPage({ params }: PageProps) {
   }
 
   return (
-    <main className="container mx-auto px-4 py-8 max-w-2xl">
+    <main className="container mx-auto px-4 sm:px-6 py-6 sm:py-8 max-w-3xl">
       {/* Header */}
-      <div className="flex items-center gap-4 mb-6">
+      <div className="flex items-center gap-3 sm:gap-4 mb-6">
         <Link
           href={`/list/${params.id}/item/${params.itemId}`}
-          className="flex items-center gap-2 text-gray-600 hover:text-gray-900 transition-colors"
+          className="flex items-center gap-2 text-gray-600 hover:text-gray-900 active:text-black transition-colors tap-target-sm text-sm sm:text-base"
         >
-          <ArrowLeft size={20} />
+          <ArrowLeft size={20} className="flex-shrink-0" />
           <span>Back</span>
         </Link>
-        <h1 className="text-2xl font-bold text-gray-900">Edit Task</h1>
+        <h1 className="text-xl sm:text-2xl lg:text-3xl font-bold text-gray-900">Edit Task</h1>
       </div>
 
       {/* Form */}
-      <div className="bg-white rounded-lg shadow-sm border border-gray-200 p-6">
+      <div className="bg-white rounded-lg shadow-sm border border-gray-200 p-5 sm:p-6 lg:p-8">
         <ItemForm listId={params.id} item={item} mode="edit" />
       </div>
     </main>