downgrade AGP and Gradle versions, update Ticker icon, and upgrade dependencies

lib/state/app/modules/app_modules.dart

@@ -54,8 +54,8 @@ class AppModule {
         Modules.ticker,
         name: 'Ticker',
         // Icons.newspaper is already taken by the "Marianum Message" module;
-        // use feed to keep the two visually distinct.
-        icon: () => Icon(Icons.feed),
+        // use campaign to keep the two visually distinct.
+        icon: () => Icon(Icons.campaign),
         breakerArea: BreakerArea.ticker,
         create: TickerView.new,
       ),