feat(task1): restructure directories for turborepo monorepo

- Move backend/ to apps/server/ via git mv
- Move frontend/ to apps/admin/ via git mv
- Create packages/typescript-config/ with base, nestjs, and react-vite presets

apps/server/src/entities/classroom.entity.ts

@@ -0,0 +1,37 @@
+import { Entity, PrimaryGeneratedColumn, Column, CreateDateColumn } from 'typeorm';
+
+@Entity('classrooms')
+export class Classroom {
+  @PrimaryGeneratedColumn()
+  id: number;
+
+  @Column({ length: 50 })
+  name: string;
+
+  @Column({ length: 50, nullable: true })
+  building: string;
+
+  @Column({ nullable: true })
+  floor: number;
+
+  @Column({ default: 30 })
+  capacity: number;
+
+  @Column({ name: 'room_type', type: 'varchar', length: 20, default: '大' })
+  roomType: string; // 大 / 次大 / 小
+
+  @Column({ name: 'course_type', length: 50, nullable: true })
+  courseType: string;
+
+  @Column({ length: 50, nullable: true })
+  supervisor: string;
+
+  @Column({ type: 'varchar', length: 20, default: 'available' })
+  status: string;
+
+  @Column({ type: 'text', nullable: true })
+  notes: string;
+
+  @CreateDateColumn({ name: 'created_at' })
+  createdAt: Date;
+}