Add DOCX export endpoint and Export button

- GET /api/export generates a Word document with all non-archived prayers
- Accepts ?status=active|answered|all and ?tag= query params to match
  the current filter/tag selection in the UI
- Document sections: Active Prayers + Answered Prayers with page break,
  each prayer showing person, request, answer, dates, and tags
- Styled with Palatino Linotype, page numbers in footer
- Export button in the toolbar triggers download of dated .docx file

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DReRqHxSYuVfCzTzQGD9hZ

package.json

@@ -12,6 +12,7 @@
     "@types/react": "^19.2.17",
     "@types/react-dom": "^19.2.3",
     "cors": "^2.8.6",
+    "docx": "^9.7.1",
     "express": "^5.2.1",
     "react": "^19.2.7",
     "react-dom": "^19.2.7",