Add attachments to comments

- CommentAttachment link table (comment <-> file) + migration
- fileIds in create/update comment; update replaces the whole set,
  synced in one transaction with the comment
- CommentDto.attachments; empty for deleted comments
- Soft delete drops attachments so GC can collect the files
- Max 10 files per comment, ordered by upload time (uuid v7)
- Registers comments as a file owner
- Rename CommentAuthorExpanderService -> CommentExpanderService
  (expands authors and files)

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

src/modules/comment/application/use-cases/test-helpers.ts

@@ -3,8 +3,9 @@ import type { ICommentRepository } from '../../domain/repositories/comment.repos
 import type { IIssueRepository } from '../../../issue/domain/repositories/issue.repository.interface.js';
 import { Comment } from '../../domain/entities/comment.entity.js';
 import { Issue } from '../../../issue/domain/entities/issue.entity.js';
-import { CommentAuthorExpanderService } from '../services/comment-author-expander.service.js';
+import { CommentExpanderService } from '../services/comment-expander.service.js';
 import { CommentApplicationMapper } from '../mappers/comment-application.mapper.js';
+import type { FileAccessService } from '../../../file/application/services/file-access.service.js';
 
 export const buildComment = (
   overrides: Partial<{ id: string; issueId: number; authorId: string; deletedAt: Date | null }> = {},
@@ -41,6 +42,8 @@ export const mockCommentRepository = (): ICommentRepository => ({
   findByIssue: vi.fn(),
   create: vi.fn(),
   update: vi.fn(),
+  findIssueIdsByAttachedFile: vi.fn(),
+  findReferencedFileIds: vi.fn(),
 });
 
 export const mockIssueRepository = (): IIssueRepository => ({
@@ -53,11 +56,20 @@ export const mockIssueRepository = (): IIssueRepository => ({
   delete: vi.fn(),
 });
 
-/** Экспандер без похода за пользователями: author всегда null */
-export const mockAuthorExpander = () => {
+/** Все файлы прикрепляемы, кроме перечисленных — для них бросается заданная ошибка */
+export const mockFileAccess = (rejections: Record<string, Error> = {}) =>
+  ({
+    getAttachableFile: vi.fn(async (fileId: string) => {
+      if (rejections[fileId]) throw rejections[fileId];
+      return { id: fileId };
+    }),
+  }) as unknown as FileAccessService;
+
+/** Экспандер без похода за пользователями и файлами: author всегда null, attachments пустые */
+export const mockCommentExpander = () => {
   const toDto = (comment: Comment) => CommentApplicationMapper.toDto(comment, new Map());
   return {
     expand: vi.fn(async (comment: Comment) => toDto(comment)),
     expandAll: vi.fn(async (comments: Comment[]) => comments.map(toDto)),
-  } as unknown as CommentAuthorExpanderService;
+  } as unknown as CommentExpanderService;
 };