feat(admin): add NSFW flag to packs, remove intensity

Re-add is_explicit toggle on pack and dare pack forms labeled as
"NSFW". Show NSFW badge on pack cards and user enabled packs.

Remove all intensity/comfort level references from admin UI including
form fields, analytics charts, review dialog columns, AI generation
prompts/scoring, cherry-pick balancing, and settings toggles. The
database columns remain unchanged.

apps/admin/src/pages/activity/UserActivityPage.tsx

@@ -440,7 +440,7 @@ export function UserActivityPage() {
     return (
         <div className="space-y-6">
             {/* Header */}
-            <div className="flex items-center justify-between">
+            <div className="flex flex-col gap-3 sm:flex-row sm:items-center sm:justify-between">
                 <div>
                     <div className="flex items-center gap-3">
                         <h1 className="text-3xl font-bold tracking-tight flex items-center gap-2">
@@ -457,7 +457,7 @@ export function UserActivityPage() {
 
             {/* Tabs */}
             <Tabs value={activeTab} onValueChange={(v) => setActiveTab(v as ActivityTab)}>
-                <TabsList className="grid w-full grid-cols-4 max-w-[600px]">
+                <TabsList className="grid w-full grid-cols-2 sm:grid-cols-4 max-w-[600px]">
                     <TabsTrigger value="responses" className="gap-2">
                         <ThumbsUp className="h-4 w-4" />
                         Responses