fix(release): automate TestFlight after standalone releases

[FelixTJDietrich]

Summary

• upload each new standalone vX.Y.Z release to TestFlight automatically
• mark successful uploads with ios-testflight@X.Y.Z so retries are idempotent
• keep App Store assets, submission, and review explicitly manual
• resolve semantic production image tags such as 5.2.0 to Git tag v5.2.0 before building the matching OTA bundle
• document the low-maintenance mobile release flow

Recovery completed

• uploaded iOS 5.2.0 build 202607270951 to TestFlight successfully
• created ios-testflight@5.2.0 after the successful upload
• confirmed production has not yet published an OTA manifest; the first approved production deploy will publish it automatically

Validation

• actionlint .github/workflows/ios-testflight-release.yml .github/workflows/ios-live-update.yml
• pnpm lint && pnpm format:check && pnpm build && pnpm test (1,751 passed, 1 skipped)

No changeset: CI/release automation and documentation only.