feat(admin): manage quiz questions and dare intensity

Add a Quiz Questions content page (list/filter/create/edit/activate-
deactivate, no delete since quiz_answers reference questions by id),
route it under manage_questions, and add a sidebar entry.

Fix DaresPage so intensity (1-5) is editable and shown in the table;
previously every admin-created dare silently defaulted to intensity 1.

Add authored min/max intensity fields to DarePacksPage: no trigger or
worker in apps/api computes these columns, so they are admin-set
thresholds gating pack visibility, not derived aggregates. avg_intensity
is displayed read-only since nothing writes to it and it is not used
for filtering.

Extract dare intensity and quiz option validation into small lib
modules with focused unit tests.

apps/admin/src/components/layout/Sidebar.tsx

@@ -21,6 +21,7 @@ import {
     PieChart,
     Tags,
     Zap,
+    HelpCircle,
 } from 'lucide-react';
 import { Button } from '@/components/ui/button';
 import { Separator } from '@/components/ui/separator';
@@ -68,6 +69,12 @@ const contentNav: NavItem[] = [
         icon: <Tags className="h-5 w-5" />,
         requiredPermission: PERMISSION_KEYS.MANAGE_PACKS,
     },
+    {
+        label: 'Quiz Questions',
+        href: '/quiz-questions',
+        icon: <HelpCircle className="h-5 w-5" />,
+        requiredPermission: PERMISSION_KEYS.MANAGE_QUESTIONS,
+    },
 ];
 
 const usersNav: NavItem[] = [