Drop lastViewedAt from uploads because inactivity cleanup is out of scope.

Add a migration and remove the column from the Upload entity.

backend/src/database/migrations/1761582000000-drop-upload-last-viewed-at.ts

@@ -0,0 +1,13 @@
+import { MigrationInterface, QueryRunner } from 'typeorm';
+
+export class DropUploadLastViewedAt1761582000000 implements MigrationInterface {
+    name = 'DropUploadLastViewedAt1761582000000';
+
+    public async up(queryRunner: QueryRunner): Promise<void> {
+        await queryRunner.query(`ALTER TABLE "uploads" DROP COLUMN "lastViewedAt"`);
+    }
+
+    public async down(queryRunner: QueryRunner): Promise<void> {
+        await queryRunner.query(`ALTER TABLE "uploads" ADD "lastViewedAt" TIMESTAMP WITH TIME ZONE`);
+    }
+}