REDI-93: host the Views list in the Compose NavHost (Compose<->View interop)

:app now owns the cross-toolkit interop. MainActivity becomes a FragmentActivity and
hosts CharacterListFragment inside the Compose NavHost via AndroidFragment at a new
@Serializable CharactersViewsRoute (defined in :app, since :app owns interop — the Views
module stays nav-agnostic). The overflow menu's 'Open as Views' / 'About' entries and the
Views item-click -> detail navigation are all injected as callbacks, keeping the renderers
decoupled. Assemble aboutPresentationModule in Koin; add androidx.fragment:fragment-compose.
The Material3 Activity theme styles both toolkits.

app/src/main/kotlin/com/example/architecture/CharactersViewsRoute.kt

@@ -0,0 +1,11 @@
+package com.example.architecture
+
+import kotlinx.serialization.Serializable
+
+/**
+ * Route for the characters list rendered with the classic **Views** toolkit. It lives in `:app`
+ * because `:app` owns Compose↔View interop — the `:feature:characters:presentation-views` module
+ * stays navigation-agnostic (it knows nothing about Compose Navigation or this route).
+ */
+@Serializable
+data object CharactersViewsRoute