Add a privacy page, and keep the map cache out of the app's backup

[octopranav]

What changes

Website

• New page, /privacy. It covers what the site and the Android app send, to whom, and what they keep on the device. Every line is taken from the code:
  • GitHub Pages serves the site.
  • api.country.is, or get.geojs.io as a fallback, receives the IP address at most weekly, for the front page's country. A blocked lookup falls back to the time zone and language, which stay in the browser.
  • OpenFreeMap serves the map tiles.
  • The site's own name index and landmark files are read from this site, so the host sees which part of the index or which area's file.
  • Kept in the browser: three settings, plus the offline caches.
  • The app: location only on request and never sent anywhere; the same two hosts; what is kept on the device and what is backed up. Share and Copy work only when pressed. Read aloud uses the device's speech engine, which may use its provider.
• The footer links to it.

Android app

• A "Privacy" link at the end of the panel opens the page in the browser. The store requires an in-app link for apps that read location. The app claims only /play links, so the page is not captured by the app itself. PRIVACY_ADDRESS lives in core, with a test that it stays outside /play.
• Backup fix. MapLibre keeps its tile cache, files/mbgl-offline.db, in the app's own files. Android's backup takes that folder by default, and the cache may grow to 200 MB. A cloud backup over 25 MB is refused whole, so the saved places the README promises a new phone would have been lost with it. res/xml/data_extraction_rules.xml (Android 12 and later) and res/xml/backup_rules.xml (earlier) now exclude the cache and its SQLite side files.

Checks

• Site:
  • Type check clean; the build lists /privacy in the sitemap.
  • In the browser, the text reads correctly. Astro's HTML compression had dropped four spaces before inline links and code; they are fixed with {' '}, as the footer does.
  • At 375 px wide in light mode: no sideways scroll and no console errors.
  • The GitHub privacy statement link resolves.
• App:
  • Core tests pass.
  • On the emulator, the link opened Chrome, at its first-run screen, which was not clicked through.
  • Backup rules: a bmgr backupnow through the local transport, with the backup rule parser's logging on, showed the four excludes. It measured only saved-places.json and preferences.xml: success, about 6 KB, the cache left out. The emulator's backup was switched back off afterwards.
• The audits, the token and icon checks, and the scan for rival names and dashes all pass.