feat(m6): board with threads/comments, markdown, tests, e2e

- BoardRepository (thread/comment CRUD, soft-delete, search, pagination,
  pinned-first ordering) + BoardService (membership permission,
  author/admin edit/delete, comment->board_commented notification,
  board_posted/comment_added activity logs, category validation)
- APIs: threads list/create/detail/edit/delete, comments create/edit/delete
- MarkdownBody (react-markdown + remark-gfm + rehype-sanitize),
  ThreadForm, CommentForm, board list + thread detail screens, ProjectNav link
- Unit tests (BoardRepository, BoardService) + e2e board.spec

app/api/projects/[projectId]/board/threads/[threadId]/route.ts

@@ -0,0 +1,75 @@
+import { NextRequest, NextResponse } from 'next/server';
+import { getCurrentUser } from '@/lib/auth/getCurrentUser';
+import { createBoardService } from '@/lib/api/services';
+import { UnauthorizedError } from '@/lib/errors';
+import { handleApiError, jsonError } from '@/lib/api/handleError';
+
+export const runtime = 'nodejs';
+
+export async function GET(
+  _request: NextRequest,
+  { params }: { params: Promise<{ projectId: string; threadId: string }> }
+) {
+  const user = await getCurrentUser();
+  if (!user) return handleApiError(new UnauthorizedError());
+  const { threadId } = await params;
+
+  const service = createBoardService();
+  try {
+    const thread = service.getThread(user.id, Number(threadId));
+    const comments = service.listComments(user.id, Number(threadId));
+    return NextResponse.json({ thread, comments });
+  } catch (error) {
+    return handleApiError(error);
+  }
+}
+
+export async function PATCH(
+  request: NextRequest,
+  { params }: { params: Promise<{ projectId: string; threadId: string }> }
+) {
+  const user = await getCurrentUser();
+  if (!user) return handleApiError(new UnauthorizedError());
+  const { threadId } = await params;
+  let body: Record<string, unknown>;
+  try {
+    body = (await request.json()) as Record<string, unknown>;
+  } catch {
+    return jsonError(400, 'リクエスト本文が不正です');
+  }
+
+  const service = createBoardService();
+  try {
+    const thread = service.updateThread(user.id, Number(threadId), {
+      title: typeof body.title === 'string' ? body.title : undefined,
+      bodyMd: typeof body.bodyMd === 'string' ? body.bodyMd : undefined,
+      category:
+        typeof body.category === 'string'
+          ? (body.category as never)
+          : undefined,
+      isPinned: typeof body.isPinned === 'number' ? body.isPinned : undefined,
+      isImportant:
+        typeof body.isImportant === 'number' ? body.isImportant : undefined,
+    });
+    return NextResponse.json({ thread });
+  } catch (error) {
+    return handleApiError(error);
+  }
+}
+
+export async function DELETE(
+  _request: NextRequest,
+  { params }: { params: Promise<{ projectId: string; threadId: string }> }
+) {
+  const user = await getCurrentUser();
+  if (!user) return handleApiError(new UnauthorizedError());
+  const { threadId } = await params;
+
+  const service = createBoardService();
+  try {
+    service.deleteThread(user.id, Number(threadId));
+    return NextResponse.json({ ok: true });
+  } catch (error) {
+    return handleApiError(error);
+  }
+}