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/occupancy.entity.ts

@@ -0,0 +1,44 @@
+import { Entity, PrimaryGeneratedColumn, Column, CreateDateColumn, ManyToOne, JoinColumn } from 'typeorm';
+import { Student } from './student.entity';
+import { Room } from './room.entity';
+
+@Entity('occupancies')
+export class Occupancy {
+  @PrimaryGeneratedColumn()
+  id: number;
+
+  @Column({ name: 'student_id' })
+  studentId: number;
+
+  @Column({ name: 'room_id' })
+  roomId: number;
+
+  @Column({ name: 'check_in_date', type: 'date' })
+  checkInDate: string;
+
+  @Column({ name: 'check_out_date', type: 'date', nullable: true })
+  checkOutDate: string;
+
+  @Column({ name: 'billing_start_date', type: 'date' })
+  billingStartDate: string;
+
+  @Column({ name: 'billing_end_date', type: 'date', nullable: true })
+  billingEndDate: string;
+
+  @Column({ name: 'check_out_reason', length: 100, nullable: true })
+  checkOutReason: string;
+
+  @Column({ type: 'text', nullable: true })
+  notes: string;
+
+  @CreateDateColumn({ name: 'created_at' })
+  createdAt: Date;
+
+  @ManyToOne(() => Student, (s) => s.occupancies)
+  @JoinColumn({ name: 'student_id' })
+  student: Student;
+
+  @ManyToOne(() => Room, (r) => r.occupancies)
+  @JoinColumn({ name: 'room_id' })
+  room: Room;
+}