Fix clean-install permission loading loop

[anilbeesetti]

Summary

• show the storage permission flow before media loading state can block it
• start media collection when permission changes from denied to granted, including grants from Android Settings
• add Android 16 Robolectric regressions for clean installs and Settings-return grants

Reproduction

On a fresh install without READ_MEDIA_VIDEO, MediaPickerViewModel correctly waits for permission and remains in DataState.Loading. The permission UI was nested under DataState.Success, so the app displayed an endless spinner and could never request the permission needed to leave Loading.

Testing

• ./gradlew :feature:videopicker:testDebugUnitTest
• ./gradlew :feature:videopicker:ktlintCheck
• ./gradlew :app:compileDebugKotlin
• clean-install flow verified on an isolated Android 16 emulator: permission prompt displayed, grant opened the media library, and crash log remained empty

Closes #1820