fix: LOW priority — GPU hints, CSRF cleanup, redundant query removal, mobile perf

- Add will-change to .hero-glow-orb (filter, transform) and .team-card-glitter::before (background-position)
- Clear CSRF cookie on logout alongside auth cookie
- Add max array length (100) validation on team reorder endpoint
- Remove redundant isOpenDayClassBookedByPhone pre-check (DB UNIQUE constraint handles it)
- Extract Schedule grid layout calculation into useMemo
- Reduce HeroLogo sparkle animations on mobile (15 → 8 via hidden sm:block)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/app/api/admin/team/reorder/route.ts

@@ -5,8 +5,8 @@ import { revalidatePath } from "next/cache";
 export async function PUT(request: NextRequest) {
   const { ids } = await request.json() as { ids: number[] };
 
-  if (!Array.isArray(ids) || ids.length === 0 || !ids.every((id) => Number.isInteger(id) && id > 0)) {
-    return NextResponse.json({ error: "ids must be a non-empty array of positive integers" }, { status: 400 });
+  if (!Array.isArray(ids) || ids.length === 0 || ids.length > 100 || !ids.every((id) => Number.isInteger(id) && id > 0)) {
+    return NextResponse.json({ error: "ids must be a non-empty array of positive integers (max 100)" }, { status: 400 });
   }
 
   reorderTeamMembers(ids);