feat: implement backend label print agent system for remote label rendering and job management

paperless-backend/src/database/entities/label-print-job.entity.ts

@@ -0,0 +1,51 @@
+import {
+  Entity,
+  PrimaryGeneratedColumn,
+  Column,
+  CreateDateColumn,
+} from 'typeorm';
+
+@Entity('label_print_jobs')
+export class LabelPrintJob {
+  @PrimaryGeneratedColumn()
+  Id!: number;
+
+  @Column({ type: 'varchar', length: 20, default: 'pending' })
+  Status!: 'pending' | 'printed' | 'error';
+
+  @Column({ type: 'mediumblob', nullable: true })
+  LabelImageData!: Buffer | null;
+
+  @Column({ type: 'int' })
+  LabelWidthMm!: number;
+
+  @Column({ type: 'int' })
+  LabelHeightMm!: number;
+
+  @Column({ type: 'int', nullable: true })
+  BarcodeTemplateId!: number | null;
+
+  @Column({ type: 'json', nullable: true })
+  LabelVariables!: Record<string, string> | null;
+
+  @Column({ type: 'datetime', nullable: true })
+  LockedAt!: Date | null;
+
+  @Column({ type: 'varchar', length: 255, nullable: true })
+  LockedByAgent!: string | null;
+
+  @Column({ type: 'datetime', nullable: true })
+  PrintedAt!: Date | null;
+
+  @Column({ type: 'varchar', length: 255, nullable: true })
+  PrintedByAgent!: string | null;
+
+  @Column({ type: 'varchar', length: 255, nullable: true })
+  PrinterName!: string | null;
+
+  @Column({ type: 'text', nullable: true })
+  ErrorMessage!: string | null;
+
+  @CreateDateColumn()
+  CreatedAt!: Date;
+}