Import source: app/backend/src/db

Import the existing local project snapshot. This commit organizes existing files; it does not represent newly developed functionality.

app/backend/src/db.ts

@@ -0,0 +1,13 @@
+// Prisma client singleton. Use this everywhere — never `new PrismaClient()` in
+// route handlers, or you'll exhaust connection slots on hot reload.
+import { PrismaClient } from '@prisma/client';
+
+const globalForPrisma = globalThis as unknown as { prisma?: PrismaClient };
+
+export const prisma =
+  globalForPrisma.prisma ??
+  new PrismaClient({
+    log: process.env.NODE_ENV === 'production' ? ['warn', 'error'] : ['query', 'warn', 'error'],
+  });
+
+if (process.env.NODE_ENV !== 'production') globalForPrisma.prisma = prisma;