[RELEASE-007] Keep Android nightly install-source checks compatible with API 26

[veryCrunchy]

User problem

Android is unavailable in otherwise successful nightly releases because release lint rejects an API 30 install-source property while the app supports Android API 26.

Failure

AndroidProjectContentClient.support() reads InstallSourceInfo.installingPackageName after storing the API-guarded object in a nullable variable. Android lint does not retain the SDK guard across that variable and fails :androidApp:lintRelease with NewApi.

Affected nightly run: https://github.com/Obiente/nc-native/actions/runs/30241981541

Acceptance criteria

• Install-source detection accesses API 30+ properties only inside an SDK-recognized guarded path.
• API 26-29 retain the deprecated installer-package fallback without crashing.
• Focused unit tests cover direct APK and store-installed channel classification.
• :androidApp:lintRelease and the signed nightly Android build path pass.
• Normal Android-changing PR checks exercise the release-lint gate before nightly publication.

Relationships

Follow-up to #178. Part of #16.