Add issue attachments

- IssueAttachment link table (issue <-> file) + migration
- GET/POST /issues/:issueId/attachments, DELETE .../attachments/:fileId
- Only own uploaded files can be attached; attach is idempotent
- Registers issues as a file owner: attached files stay visible to issue
  participants and are not collected by GC
- IssueDetail.attachments GraphQL field via @ResolveField, issue module untouched

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

src/modules/issue-attachment/infrastructure/persistence/prisma/mappers/issue-attachment.mapper.ts

@@ -0,0 +1,20 @@
+import type { IssueAttachment as PrismaIssueAttachment, Prisma } from '../../../../../../generated/prisma/client.js';
+import { IssueAttachment } from '../../../../domain/entities/issue-attachment.entity.js';
+
+export class IssueAttachmentPrismaMapper {
+  static toDomain(record: PrismaIssueAttachment): IssueAttachment {
+    return IssueAttachment.reconstitute({
+      issueId: record.issueId,
+      fileId: record.fileId,
+      createdAt: record.createdAt,
+    });
+  }
+
+  static toCreateInput(attachment: IssueAttachment): Prisma.IssueAttachmentUncheckedCreateInput {
+    return {
+      issueId: attachment.issueId,
+      fileId: attachment.fileId,
+      createdAt: attachment.createdAt,
+    };
+  }
+}

src/modules/issue-attachment/infrastructure/persistence/prisma/repositories/issue-attachment.prisma-repository.ts

@@ -0,0 +1,70 @@
+import { Injectable } from '@nestjs/common';
+import { PrismaAdapter } from '../../../../../../common/prisma-adapter/prisma.adapter.js';
+import { Prisma } from '../../../../../../generated/prisma/client.js';
+import { IssueAttachment } from '../../../../domain/entities/issue-attachment.entity.js';
+import { IIssueAttachmentRepository } from '../../../../domain/repositories/issue-attachment.repository.interface.js';
+import { IssueAttachmentPrismaMapper } from '../mappers/issue-attachment.mapper.js';
+import { IssueNotFoundException } from '../../../../../issue/domain/exceptions/issue-not-found.exception.js';
+import { FileNotFoundException } from '../../../../../file/domain/exceptions/file-not-found.exception.js';
+
+const FOREIGN_KEY_VIOLATION = 'P2003';
+
+@Injectable()
+export class IssueAttachmentPrismaRepository implements IIssueAttachmentRepository {
+  constructor(private readonly prisma: PrismaAdapter) {}
+
+  async findByIssue(issueId: number): Promise<IssueAttachment[]> {
+    const records = await this.prisma.issueAttachment.findMany({
+      where: { issueId },
+      orderBy: [{ createdAt: 'asc' }, { fileId: 'asc' }],
+    });
+    return records.map(IssueAttachmentPrismaMapper.toDomain);
+  }
+
+  async findIssueIdsByFile(fileId: string): Promise<number[]> {
+    const records = await this.prisma.issueAttachment.findMany({
+      where: { fileId },
+      select: { issueId: true },
+    });
+    return records.map((record) => record.issueId);
+  }
+
+  async findReferencedFileIds(fileIds: string[]): Promise<string[]> {
+    if (fileIds.length === 0) return [];
+
+    const records = await this.prisma.issueAttachment.findMany({
+      where: { fileId: { in: fileIds } },
+      select: { fileId: true },
+      distinct: ['fileId'],
+    });
+    return records.map((record) => record.fileId);
+  }
+
+  async create(attachment: IssueAttachment): Promise<IssueAttachment> {
+    try {
+      // upsert с пустым update — идемпотентное прикрепление без гонки «проверил — вставил»
+      const record = await this.prisma.issueAttachment.upsert({
+        where: { issueId_fileId: { issueId: attachment.issueId, fileId: attachment.fileId } },
+        create: IssueAttachmentPrismaMapper.toCreateInput(attachment),
+        update: {},
+      });
+
+      return IssueAttachmentPrismaMapper.toDomain(record);
+    } catch (error) {
+      // Задачу или файл удалили между проверкой доступа и вставкой.
+      // Какой именно FK нарушен — по имени ограничения в meta
+      if (error instanceof Prisma.PrismaClientKnownRequestError && error.code === FOREIGN_KEY_VIOLATION) {
+        if (JSON.stringify(error.meta ?? {}).includes('fileId')) {
+          throw new FileNotFoundException(attachment.fileId);
+        }
+        throw new IssueNotFoundException(attachment.issueId);
+      }
+      throw error;
+    }
+  }
+
+  async delete(issueId: number, fileId: string): Promise<boolean> {
+    const { count } = await this.prisma.issueAttachment.deleteMany({ where: { issueId, fileId } });
+    return count > 0;
+  }
+}