feat: stabilize admin dashboard, refactor group management, implement PWA, and fix routing

app/server/api/groups/index.get.ts

@@ -5,7 +5,7 @@ export default defineEventHandler(async (event) => {
   const user = requireAuth(event)
 
   const allGroups = await prisma.group.findMany({
-    where: { isPublic: true },
+    where: user.role === 'admin' ? {} : { isPublic: true },
     include: {
       members: { include: { user: { select: { id: true, username: true } } } },
       _count: { select: { members: true, canvases: true } }