Add file module for uploads and storage

- File model + migration: file metadata, content lives in object storage
- IFileStorage port with local disk and S3-compatible (RustFS/MinIO) adapters
- POST /files, GET /files/:id/download, DELETE /files/:id
- MIME sniffed from content; only safe images served inline, nosniff header
- FileOwnerRegistry: owner modules register to grant visibility and keep
  their files from GC; FileGcService removes orphaned files hourly
- TransformResponseInterceptor passes StreamableFile through

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/modules/file/application/use-cases/get-files/get-files.use-case.ts

@@ -0,0 +1,24 @@
+import { Inject, Injectable } from '@nestjs/common';
+import { FILE_REPOSITORY, type IFileRepository } from '../../../domain/repositories/file.repository.interface.js';
+import { GetFilesQuery } from './get-files.query.js';
+import { FileDto } from '../../dto/file.dto.js';
+import { FileApplicationMapper } from '../../mappers/file-application.mapper.js';
+
+/**
+ * Метаданные файлов по id — для модулей-владельцев, раскрывающих свои связи
+ * в FileDto (по аналогии с GetUsersUseCase). Доступ проверяет вызывающий:
+ * он отдаёт только файлы своих сущностей, видимых пользователю.
+ */
+@Injectable()
+export class GetFilesUseCase {
+  constructor(
+    @Inject(FILE_REPOSITORY)
+    private readonly fileRepository: IFileRepository,
+  ) {}
+
+  async execute(query: GetFilesQuery): Promise<FileDto[]> {
+    const ids = [...new Set(query.ids)];
+    const files = await this.fileRepository.findByIds(ids);
+    return files.map(FileApplicationMapper.toDto);
+  }
+}