feat(chat,board): file/image attachments on chat, board threads and comments

チャット・掲示板(スレッド/コメント)へファイル/画像添付を追加。

- lib/db/migrations/002_attachments.sql: attachments テーブル + file_assets.source 列
- repositories/AttachmentRepository + services/AttachmentService: 添付紐付け(プロジェクト/アップロード者チェック)
- FileStorageService.uploadForAttachment: 通知/SSE/アクティビティを行わない添付専用アップロード(source='attachment')
- ChatService/BoardService: fileIds 受理・添付紐付け・履歴/詳細表示・削除クリーンアップ(トランザクション)
- API: POST /attachments + chat/board の fileIds 受理
- UI: AttachmentList(画像サムネイル+Lightbox/ダウンロード) + AttachmentPicker(複数アップロード・送信中は送信不可) をチャット/スレッド/コメントに統合
- 添付ファイルは既存の /api/files/[fileId]/download(権限チェック済)で配信

repositories/AttachmentRepository.ts

@@ -0,0 +1,135 @@
+import type { SqliteDatabase } from '@/lib/db/sqlite';
+import type {
+  Attachment,
+  AttachmentTargetType,
+  AttachmentView,
+} from '@/lib/types';
+
+interface AttachmentRow {
+  id: number;
+  project_id: number;
+  file_id: number;
+  target_type: string;
+  target_id: number;
+  created_at: string;
+  deleted_at: string | null;
+}
+
+interface AttachmentViewRow {
+  id: number;
+  file_id: number;
+  target_type: string;
+  target_id: number;
+  original_name: string;
+  mime_type: string;
+  size: number;
+}
+
+function mapAttachment(row: AttachmentRow): Attachment {
+  return {
+    id: row.id,
+    projectId: row.project_id,
+    fileId: row.file_id,
+    targetType: row.target_type as AttachmentTargetType,
+    targetId: row.target_id,
+    createdAt: row.created_at,
+    deletedAt: row.deleted_at,
+  };
+}
+
+function mapView(row: AttachmentViewRow): AttachmentView {
+  return {
+    id: row.id,
+    fileId: row.file_id,
+    targetType: row.target_type as AttachmentTargetType,
+    targetId: row.target_id,
+    originalName: row.original_name,
+    mimeType: row.mime_type,
+    size: row.size,
+  };
+}
+
+export interface CreateAttachmentInput {
+  projectId: number;
+  fileId: number;
+  targetType: AttachmentTargetType;
+  targetId: number;
+}
+
+/**
+ * attachments テーブルのCRUDを担うRepository。
+ * file_assets とJOINして表示用ビューを返す。
+ */
+export class AttachmentRepository {
+  constructor(private readonly db: SqliteDatabase) {}
+
+  create(input: CreateAttachmentInput): Attachment {
+    const now = new Date().toISOString();
+    const result = this.db.execute(
+      `INSERT INTO attachments (project_id, file_id, target_type, target_id, created_at, deleted_at)
+       VALUES (@projectId, @fileId, @targetType, @targetId, @createdAt, NULL)`,
+      {
+        projectId: input.projectId,
+        fileId: input.fileId,
+        targetType: input.targetType,
+        targetId: input.targetId,
+        createdAt: now,
+      }
+    );
+    const created = this.findById(Number(result.lastInsertRowid));
+    if (!created) throw new Error('Failed to create attachment');
+    return created;
+  }
+
+  findById(id: number): Attachment | null {
+    const row = this.db.get<AttachmentRow>(
+      'SELECT * FROM attachments WHERE id = @id AND deleted_at IS NULL',
+      { id }
+    );
+    return row ? mapAttachment(row) : null;
+  }
+
+  findByTarget(
+    targetType: AttachmentTargetType,
+    targetId: number
+  ): Attachment[] {
+    const rows = this.db.query<AttachmentRow>(
+      `SELECT * FROM attachments
+       WHERE target_type = @targetType AND target_id = @targetId AND deleted_at IS NULL
+       ORDER BY id ASC`,
+      { targetType, targetId }
+    );
+    return rows.map(mapAttachment);
+  }
+
+  /** 複数ターゲットの添付ビューを一括取得(N+1回避)。 */
+  findViewsByTargets(
+    targetType: AttachmentTargetType,
+    targetIds: number[]
+  ): AttachmentView[] {
+    if (targetIds.length === 0) return [];
+    const placeholders = targetIds.map(() => '?').join(',');
+    const rows = this.db.query<AttachmentViewRow>(
+      `SELECT a.id AS id, a.file_id AS file_id, a.target_type AS target_type,
+              a.target_id AS target_id, f.original_name AS original_name,
+              f.mime_type AS mime_type, f.size AS size
+         FROM attachments a
+         JOIN file_assets f ON f.id = a.file_id
+        WHERE a.target_type = ? AND a.deleted_at IS NULL
+          AND f.deleted_at IS NULL
+          AND a.target_id IN (${placeholders})
+        ORDER BY a.target_id ASC, a.id ASC`,
+      [targetType, ...targetIds]
+    );
+    return rows.map(mapView);
+  }
+
+  /** 対象の添付を論理削除(メッセージ/スレッド/コメント削除時のクリーンアップ)。 */
+  deleteByTarget(targetType: AttachmentTargetType, targetId: number): boolean {
+    const result = this.db.execute(
+      'UPDATE attachments SET deleted_at = @now WHERE target_type = @targetType AND target_id = @targetId AND deleted_at IS NULL',
+      { now: new Date().toISOString(), targetType, targetId }
+    );
+    return result.changes > 0;
+  }
+}