feat(m10): file sharing with upload, lightbox, permission, tests, e2e

- FileRepository (CRUD, soft-delete, pagination, project isolation) +
  FileStorageService (local FS save data/uploads/<projectId>/<uuid>.<ext>,
  MIME allowlist, filename sanitize, unique uuid name, member permission,
  file_shared notification to other members, file_uploaded activity log,
  SSE file.uploaded, uploader/admin delete + FS unlink)
- APIs: files list/upload(multipart), download (membership), delete
- Screens: files page + Uploader(multipart) + FileList(image Lightbox,
  PDF link, delete), ProjectNav ファイル link
- Unit tests (FileRepository, FileStorageService) + e2e file-sharing

app/api/projects/[projectId]/files/route.ts

@@ -0,0 +1,55 @@
+import { NextRequest, NextResponse } from 'next/server';
+import { getCurrentUser } from '@/lib/auth/getCurrentUser';
+import { createFileStorageService } from '@/lib/api/services';
+import { UnauthorizedError, ValidationError } from '@/lib/errors';
+import { handleApiError } from '@/lib/api/handleError';
+
+export const runtime = 'nodejs';
+
+export async function GET(
+  request: NextRequest,
+  { params }: { params: Promise<{ projectId: string }> }
+) {
+  const user = await getCurrentUser();
+  if (!user) return handleApiError(new UnauthorizedError());
+  const { projectId } = await params;
+  const page = Number(request.nextUrl.searchParams.get('page') ?? '1') || 1;
+  const service = createFileStorageService();
+  try {
+    return NextResponse.json(
+      service.listFiles(user.id, Number(projectId), page)
+    );
+  } catch (error) {
+    return handleApiError(error);
+  }
+}
+
+export async function POST(
+  request: NextRequest,
+  { params }: { params: Promise<{ projectId: string }> }
+) {
+  const user = await getCurrentUser();
+  if (!user) return handleApiError(new UnauthorizedError());
+  const { projectId } = await params;
+
+  const formData = await request.formData();
+  const file = formData.get('file');
+  if (!(file instanceof File)) {
+    return handleApiError(
+      new ValidationError('ファイルを指定してください', 'file')
+    );
+  }
+
+  const data = Buffer.from(await file.arrayBuffer());
+  const service = createFileStorageService();
+  try {
+    const fileAsset = service.upload(user.id, Number(projectId), {
+      originalName: file.name,
+      mimeType: file.type || 'application/octet-stream',
+      data,
+    });
+    return NextResponse.json({ file: fileAsset }, { status: 201 });
+  } catch (error) {
+    return handleApiError(error);
+  }
+}