feat: add ClassesService with CRUD + student/teacher management

apps/server/src/classes/classes.module.ts

@@ -0,0 +1,12 @@
+import { Module } from '@nestjs/common';
+import { TypeOrmModule } from '@nestjs/typeorm';
+import { Class, ClassStudent, ClassTeacher } from '../entities';
+import { ClassesService } from './classes.service';
+import { OperationLogsModule } from '../operation-logs/operation-logs.module';
+
+@Module({
+  imports: [TypeOrmModule.forFeature([Class, ClassStudent, ClassTeacher]), OperationLogsModule],
+  providers: [ClassesService],
+  exports: [ClassesService],
+})
+export class ClassesModule {}