Tighten typing and input validation across study pages

src/app/api/quizzes/reorder/route.ts

@@ -1,19 +1,20 @@
 import { NextRequest, NextResponse } from "next/server";
 import { prisma } from "@/lib/db";
+import { reorderRequestSchema } from "@/lib/validation/reorderSchemas";
 
 export async function PATCH(request: NextRequest) {
   try {
-    const body = await request.json();
-    const { items } = body;
-
-    if (!Array.isArray(items)) {
+    const parsed = reorderRequestSchema.safeParse(await request.json());
+    if (!parsed.success) {
       return NextResponse.json({ error: "Invalid input" }, { status: 400 });
     }
 
+    const { items } = parsed.data;
+
     // items should be an array of { id, sortOrder, groupId }
     // Using a transaction to perform all updates
     await prisma.$transaction(
-      items.map((item: any) =>
+      items.map((item) =>
         prisma.quizSet.update({
           where: { id: item.id },
           data: {