feat(server): add auth, user, and studio modules

Auth: WeChat login, JWT, roles guard (24 tests passing)
User: profile CRUD, training stats with month/total calculations
Studio: config management with auto-default creation

packages/server/src/studio/studio.module.ts

@@ -0,0 +1,10 @@
+import { Module } from '@nestjs/common'
+import { StudioController } from './studio.controller'
+import { StudioService } from './studio.service'
+
+@Module({
+  controllers: [StudioController],
+  providers: [StudioService],
+  exports: [StudioService],
+})
+export class StudioModule {}