Safari blocks loading PMTiles modules from file:// URLs. Open the folder in Terminal and run one of these, then visit the printed URL:
# option 1 (recommended, supports byte-range for PMTiles)
npx http-server -p 8080 -c-1
# option 2 (Python; basemap works, PMTiles may be slow)
python3 -m http.server 8080
Then open http://localhost:8080/paddy-watcher.html in this browser, or use your machine's local IP on your phone. The hosted version at aimansukiman.com already serves correctly.