What changed

• Replaced the upgrade dialog with a dedicated full-screen upgrade screen that presents pro benefits before the purchase action
• Both FOSS (sponsor development) and Google Play (in-app purchase) flavors get their own tailored upgrade screen
• All upgrade entry points (overview toolbar, general settings, reaction settings, widget configuration) now navigate to the new screen

Technical Context

• Added per-flavor UpgradeScreen, UpgradeViewModel, and UpgradeNavigation under upgrade/ui/ packages
• Removed launchBillingFlow from UpgradeRepo interface — billing flow is now encapsulated in the gplay UpgradeViewModel via BillingDataRepo
• Widget configuration redirects non-pro users to MainActivity with a NAVIGATE_TO_UPGRADE intent extra, handled in both onCreate and onNewIntent
• gplay ViewModel auto-navigates back when isPro becomes true by observing upgradeInfo flow
• Restore purchase checks specifically for CapodSku.PRO_UPGRADE to avoid false positives from unrelated purchases