feat: Prisma 用户落库、迁移与启动环境加载

- Prisma 7 + adapter-pg；prisma.config 与 users 初始迁移\n- AppModule 挂载 PrismaModule；PrismaService 仅依赖 DATABASE_URL\n- main 入口 dotenv/config，避免 Prisma 早于 Config 读 env\n- 短信登录 upsert User；默认昵称 Chat+手机号后四位\n- README / project-solution：目录、迁移规范、用户 avatar_url 说明\n- 依赖：dotenv、@prisma/adapter-pg、pg

Made-with: Cursor

prisma/migrations/20260421164244_init_users/migration.sql

@@ -0,0 +1,15 @@
+-- CreateTable
+CREATE TABLE "users" (
+    "id" BIGSERIAL NOT NULL,
+    "phone" VARCHAR(32) NOT NULL,
+    "nickname" VARCHAR(100),
+    "avatar_url" VARCHAR(512),
+    "status" SMALLINT NOT NULL DEFAULT 1,
+    "created_at" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updated_at" TIMESTAMP(3) NOT NULL,
+
+    CONSTRAINT "users_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE UNIQUE INDEX "users_phone_key" ON "users"("phone");

prisma/migrations/migration_lock.toml

@@ -0,0 +1,3 @@
+# Please do not edit this file manually
+# It should be added in your version-control system (e.g., Git)
+provider = "postgresql"

prisma/schema.prisma

@@ -0,0 +1,19 @@
+generator client {
+  provider = "prisma-client-js"
+}
+
+datasource db {
+  provider = "postgresql"
+}
+
+model User {
+  id        BigInt   @id @default(autoincrement())
+  phone     String   @unique @db.VarChar(32)
+  nickname  String?  @db.VarChar(100)
+  avatarUrl String?  @map("avatar_url") @db.VarChar(512)
+  status    Int      @default(1) @db.SmallInt
+  createdAt DateTime @default(now()) @map("created_at")
+  updatedAt DateTime @updatedAt @map("updated_at")
+
+  @@map("users")
+}