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/logout/route.ts

@@ -1,5 +1,5 @@
 import { NextResponse } from "next/server";
-import { COOKIE_NAME } from "@/lib/auth";
+import { COOKIE_NAME, CSRF_COOKIE_NAME } from "@/lib/auth";
 
 export async function POST() {
   const response = NextResponse.json({ ok: true });
@@ -8,5 +8,9 @@ export async function POST() {
     path: "/",
     maxAge: 0,
   });
+  response.cookies.set(CSRF_COOKIE_NAME, "", {
+    path: "/",
+    maxAge: 0,
+  });
   return response;
 }