build(deps): migrate to Prisma 7 (driver adapter)

lib/prisma.ts

@@ -1,14 +1,28 @@
 import { PrismaClient } from '@prisma/client';
+import { PrismaPg } from '@prisma/adapter-pg';
 
 const globalForPrisma = globalThis as unknown as {
   prisma: PrismaClient | undefined;
 };
 
-export const prisma = globalForPrisma.prisma ?? new PrismaClient({
-  log: ['error'],
-  errorFormat: 'pretty',
-});
+const connectionString = process.env.DATABASE_URL;
+
+if (!connectionString) {
+  throw new Error('DATABASE_URL is not set');
+}
+
+// Prisma 7 connects through a driver adapter instead of a schema-level `url`.
+// PrismaPg manages its own pg connection pool from the connection string.
+const adapter = new PrismaPg({ connectionString });
+
+export const prisma =
+  globalForPrisma.prisma ??
+  new PrismaClient({
+    adapter,
+    log: ['error'],
+    errorFormat: 'pretty',
+  });
 
 if (process.env.NODE_ENV !== 'production') {
   globalForPrisma.prisma = prisma;
-} 
+}