feat(firebase): tvOS support for firebase_remote_config

[TheNoumanDev]

PR description (continuous lines)

What does this PR do?

Adds federated firebase_remote_config_tvos — Firebase Remote Config for Apple TV, built on the Firebase Apple SDK. Re-exports the firebase_remote_config Dart API and ships the native tvOS pluginClass; depends on firebase_core_tvos. Full Remote Config API (defaults, fetch/activate/fetchAndActivate, typed getters, config settings, real-time updates), no feature disables.

Package(s) touched: firebase_remote_config_tvos (new)

How was it tested?

Verified end-to-end on both the tvOS simulator and a physical Apple TV 4K (tvOS 26.2, release/AOT) against a live Firebase project. FirebaseRemoteConfig 12.15.0 initialized, a real fetch hit firebaseremoteconfig.googleapis.com/.../namespaces/firebase:fetch, and fetchAndActivate returned activated=true with lastFetchStatus == RemoteConfigFetchStatus.success. A parameter published in the Firebase console was fetched and activated on the device — the on-device RemoteConfig.sqlite3 (pulled via devicectl) holds the console value in both the fetched and active tables, overriding the local default. No feature disables (Remote Config is UI-free). Platform.operatingSystem == "tvos" / Platform.isIOS == true.

• Ran the package's example/ app
• Verified on tvOS simulator (version: 26.2) — a console-published parameter was fetched and overrode the local default (RemoteConfigFetchStatus.success)
• Verified on a physical Apple TV 4K (tvOS 26.2, release/AOT) — console-published parameter fetched + activated on-device (confirmed in the device's RemoteConfig.sqlite3)
• 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_remote_config_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_remote_config 6.5.3 on the firebase_core_platform_interface 7.1.0 train (firebase_core 4.11.x). Mixing firebase_core_tvos with a different firebase_core whose FirebaseOptions list differs can crash in CoreFirebaseOptions.fromList at launch (Dart options: init). 6.5.3 is the latest on this train — 6.5.6 requires firebase_core 4.13 / platform interface 8.1.
• Manual work beyond the auto-port: podspec deps (Firebase/RemoteConfig + firebase_core_tvos, tvOS 15); Swift firebase_core import repointed to firebase_core_tvos; generated tvos/Package.swift removed (route via podspec); Dart re-export.