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

components/files/Uploader.tsx

@@ -0,0 +1,58 @@
+'use client';
+
+import { useRef, useState } from 'react';
+import { useRouter } from 'next/navigation';
+
+export function Uploader({ projectId }: { projectId: number }) {
+  const router = useRouter();
+  const inputRef = useRef<HTMLInputElement>(null);
+  const [loading, setLoading] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+
+  async function onFile(event: React.ChangeEvent<HTMLInputElement>) {
+    const file = event.target.files?.[0];
+    if (!file) return;
+    setLoading(true);
+    setError(null);
+    const form = new FormData();
+    form.append('file', file);
+    const res = await fetch(`/api/projects/${projectId}/files`, {
+      method: 'POST',
+      body: form,
+    });
+    setLoading(false);
+    if (res.ok) {
+      if (inputRef.current) inputRef.current.value = '';
+      router.refresh();
+    } else {
+      const b = (await res.json().catch(() => null)) as {
+        error?: { message?: string };
+      } | null;
+      setError(b?.error?.message ?? 'アップロードに失敗しました');
+    }
+  }
+
+  return (
+    <div className="rounded-lg border bg-white p-4 shadow-sm">
+      <label className="block text-sm font-medium">
+        ファイルをアップロード
+      </label>
+      <input
+        ref={inputRef}
+        type="file"
+        onChange={onFile}
+        disabled={loading}
+        className="mt-2 block text-sm"
+        data-testid="file-input"
+      />
+      {loading && (
+        <p className="mt-1 text-sm text-gray-500">アップロード中...</p>
+      )}
+      {error && (
+        <p className="mt-1 text-sm text-red-600" role="alert">
+          {error}
+        </p>
+      )}
+    </div>
+  );
+}