fix: validate ID parsing in API routes and player pages for Prisma v7

src/app/api/tournaments/[id]/participants/route.ts

@@ -7,7 +7,15 @@ export async function POST(
   { params }: { params: { id: string } }
 ) {
   try {
-    const tournamentId = parseInt(params.id);
+    const tournamentId = parseInt(params.id, 10);
+    
+    if (isNaN(tournamentId)) {
+      return NextResponse.json(
+        { error: "Invalid tournament ID" },
+        { status: 400 }
+      );
+    }
+    
     const body = await request.json();
     const { playerIds } = body;