v0.5.3

Changed

• GitHub Actions: Node.js 24 migration. Bumped all actions to
  Node.js 24-compatible versions (checkout@v6, setup-java@v5,
  setup-buildx-action@v4, login-action@v4, metadata-action@v6,
  build-push-action@v7, action-gh-release@v3) ahead of the
  June 16 deprecation deadline.

Added

• Android: battery optimization prompt. The settings screen now
  shows a card when battery optimization is enabled, with a one-tap
  button to request exemption. Prevents the system from killing the
  background sync service.
• CI: "recovered" PR notification. When a CI run succeeds after a
  previous failure on the same PR, a comment is posted automatically
  so reviewers know the issue is resolved.