Add Next.js client app with Prisma and auth

Introduce a new 'client' Next.js app scaffold: configuration files (next.config.ts, eslint.config.mjs, postcss, tsconfig), Prisma config and schema, app routes including NextAuth API and server actions, session/provider utilities, proxy, public assets, README and .gitignore. Also add IDE project files under .idea and a root README to initialize the repository structure for development.

client/prisma/schema.prisma

@@ -0,0 +1,22 @@
+// This is your Prisma schema file,
+// learn more about it in the docs: https://pris.ly/d/prisma-schema
+
+// Looking for ways to speed up your queries, or scale easily with your serverless or edge functions?
+// Try Prisma Accelerate: https://pris.ly/cli/accelerate-init
+
+generator client {
+  provider = "prisma-client"
+  output   = "../src/generated/prisma"
+}
+
+datasource db {
+  provider = "postgresql"
+}
+
+model user{
+  id        String   @id @default(uuid())
+  email     String   @unique
+  name      String?
+  createdAt DateTime @default(now())
+  updatedAt DateTime @updatedAt
+}