feat(firebase): tvOS support for firebase_crashlytics

[TheNoumanDev]

What does this PR do?

Adds federated firebase_crashlytics_tvos — Firebase Crashlytics for Apple TV, built on the Firebase Apple SDK. Re-exports the firebase_crashlytics Dart API and ships the native tvOS pluginClass; depends on firebase_core_tvos. Full Crashlytics API, no feature disables.

Package(s) touched: firebase_crashlytics_tvos (new)

How was it tested?

Verified against a live Firebase project on both the tvOS simulator and a
physical Apple TV 4K (release/AOT): initializeApp(options:) succeeds, [Firebase/Crashlytics] 12.15.0 starts and fetches settings from …/platforms/tvos/gmp/<app-id>/settings, and a forced FirebaseCrashlytics.instance.crash() was captured and reported to the Crashlytics console on both (uploaded to crashlyticsreports-pa.googleapis.com, appeared as a crash issue). Platform.operatingSystem == "tvos" / Platform.isIOS == true.

• Ran the package's example/ app
• Verified on tvOS simulator (version: 26.2) — forced crash reached the Crashlytics console
• Verified on a physical Apple TV 4K (tvOS 26.2, release/AOT) — forced crash reported to the console (dSYM symbolication is the usual app-side build config, same as iOS)
• dart analyze is clean for the package

Versioning & changelog

• version: set to 0.0.1 (new package)
• Matching ## 0.0.1 entry at the top of CHANGELOG.md
• No behaviour change (new package)
• Semver 0.x: initial 0.0.1

Checklist

• Only firebase_crashlytics_tvos files are touched
• No secrets, absolute local paths, or TODO/debug leftovers
• README.md documents tvOS behaviour (no feature limitations; version-alignment note)
• Sibling-package constraint noted below

Notes for reviewers

• Version alignment (affects all Firebase _tvos leaf packages): the native code matches firebase_crashlytics 5.2.4 on the firebase_core_platform_interface 7.1.0 train (firebase_core 4.11.x) — this is the latest Crashlytics on that train (5.2.7+ moves to firebase_core 4.13.0 / platform_interface 8.1.0, which the published firebase_core_tvos isn't built for).
• Manual work beyond the auto-port: podspec deps (Firebase/Crashlytics + firebase_core_tvos, tvOS 15, LIBRARY_NAME defines); <firebase_core/…> imports repointed to <firebase_core_tvos/…>; Dart re-export.

[TheNoumanDev]

Hey @MAUstaoglu @DenisovAV — this adds firebase_crashlytics_tvos . Would appreciate a review whenever you have time — thanks!