feat: add Prisma configuration file and update Dockerfile to include it

backend/prisma.config.ts

@@ -0,0 +1,11 @@
+import { defineConfig } from 'prisma/config';
+
+export default defineConfig({
+  schema: 'prisma/schema.prisma',
+  migrations: {
+    path: 'prisma/migrations',
+  },
+  datasource: {
+    url: process.env.DATABASE_URL!,
+  },
+});