fix(release): prepare version 278 for play resubmission

[zfdang]

Summary

Prepare version 278 for Google Play resubmission with an accessible, accurate privacy policy and a version code higher than previously distributed APKs.

Changes

• Explain local custom rules, clipboard export, consent, deletion and Android system backup in both policy languages.
• Add a clickable privacy policy link to the About screen.
• Set the release versionCode to 278; Git commit counts can shrink after squash merges.
• Derive release tags from APK metadata and publish GitHub releases only on master pushes.

Verification

• 66 debug unit tests passed.
• Release lint passed with no errors (existing warnings remain).
• Signed release AAB and APK built successfully with JDK 17.