feat: top app bar title updates based on current route (Closes #22)

TopAppBar title now reflects the current NavController destination:
character sheet shows the character name, settings shows "Settings",
fallback shows the app name. Uses currentRoute() helper already
available from NavHost integration.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sharedUI/src/commonMain/kotlin/org/shahondin1624/App.kt

@@ -240,12 +240,19 @@ private fun MainScaffold(
     modifier: Modifier = Modifier
 ) {
     var isDark by LocalThemeIsDark.current
+    val currentRoute = currentRoute(navController)
+
+    val topBarTitle = when (currentRoute) {
+        AppRoutes.CHARACTER_SHEET -> EXAMPLE_CHARACTER.characterData.name
+        AppRoutes.SETTINGS -> "Settings"
+        else -> "Shadowrun Character Sheet"
+    }
 
     Scaffold(
         modifier = modifier.fillMaxSize(),
         topBar = {
             TopAppBar(
-                title = { Text("Shadowrun Character Sheet") },
+                title = { Text(topBarTitle) },
                 modifier = Modifier.testTag(TestTags.TOP_APP_BAR),
                 navigationIcon = {
                     if (showMenuButton) {