fix: update PrismaService constructor to include datasourceUrl configuration

backend/src/prisma/prisma.service.ts

@@ -9,7 +9,7 @@ export class PrismaService
   private readonly logger = new Logger(PrismaService.name);
 
   constructor() {
-    super();
+    super({ datasourceUrl: process.env.DATABASE_URL });
   }
 
   async onModuleInit() {