feat: phase 1 — auth + user endpoints, Prisma v7 adapter, DB init

backend/src/validators/user.validators.ts

@@ -0,0 +1,9 @@
+import { z } from "zod";
+
+export const updateUserSchema = z.object({
+  username: z.string().min(3).max(20).optional(),
+  bio: z.string().max(300).optional(),
+  avatar: z.string().url().optional(),
+});
+
+export type UpdateUserInput = z.infer<typeof updateUserSchema>;