feat: add About & FOSS screen with Android 17 specs and fix rapid call launch state sync

- Add comprehensive AboutScreen with app metadata, developer details (Ryan Shelby), support email, and FOSS repository links
- Dynamically resolve Target SDK (Android 17 / API 37) and running OS in diagnostic specifications card and exportable report
- Fix rapid call button / Call Now clicking race condition with UI debouncing and immediate optimistic call tracking in CallManager
- Ensure Telecom notification and in-call screen sync cleanly on fast-dialed calls