feat: update components for multi-user support

- Add sharing indicator to ListCard showing collaborator count
- Add permission badge and share button to ListDetailView
- Disable editing in ItemForm for viewers with visual feedback
- Add permission checks to item detail and edit pages
- Hide edit/delete buttons for viewers on item detail page
- Pass permission and collaborator data through component hierarchy
- Update navigation to include profile and invitations links (already done in previous tasks)

Implements task 15 from user-auth-and-sharing spec

app/list/[id]/page.tsx

@@ -1,4 +1,6 @@
 import { getListWithItems } from '@/lib/actions'
+import { getPermission } from '@/lib/permissions'
+import { auth } from '@/auth'
 import { notFound } from 'next/navigation'
 import Link from 'next/link'
 import { ArrowLeft } from 'lucide-react'
@@ -8,12 +10,25 @@ import ListDetailView from '@/components/ListDetailView'
 export const dynamic = 'force-dynamic'
 
 export default async function ListDetailPage({ params }: { params: { id: string } }) {
+  const session = await auth()
+  if (!session?.user?.id) {
+    notFound()
+  }
+
   const list = await getListWithItems(params.id)
 
   if (!list) {
     notFound()
   }
 
+  // Get user's permission for this list
+  const permission = await getPermission(session.user.id, params.id)
+  if (!permission) {
+    notFound()
+  }
+
+  const canShare = permission === 'owner'
+  const canEdit = permission === 'owner' || permission === 'editor'
   const completedItems = list.items.filter(item => item.completed)
 
   return (
@@ -41,13 +56,28 @@ export default async function ListDetailPage({ params }: { params: { id: string
         </p>
       </div>
 
-      {/* Inline Item Creation */}
-      <div className="mb-6 sm:mb-8">
-        <InlineItemCreate listId={list.id} />
-      </div>
+      {/* Inline Item Creation - only show if user can edit */}
+      {canEdit && (
+        <div className="mb-6 sm:mb-8">
+          <InlineItemCreate listId={list.id} />
+        </div>
+      )}
 
       {/* Search, Filter, and Items List */}
-      <ListDetailView listId={list.id} initialItems={list.items} />
+      <ListDetailView 
+        listId={list.id} 
+        initialItems={list.items}
+        permission={permission}
+        canShare={canShare}
+        listTitle={list.title}
+        ownerId={list.ownerId}
+        ownerName={list.owner?.name}
+        ownerEmail={list.owner?.email || ''}
+        collaborators={list.collaborators.map(c => ({
+          ...c,
+          permission: c.permission as 'editor' | 'viewer'
+        }))}
+      />
     </main>
   )
 }