feat(characters): Koin module + nav graph + wire into :app (REDI-89)

- charactersPresentationModule: viewModelOf(::CharacterListViewModel) (in the UI-agnostic module).
- @Serializable CharacterListRoute + NavGraphBuilder.charactersGraph { composable<CharacterListRoute> }
  in presentation-compose (serialization plugin added for type-safe routes).
- :app registers coreDataModule + charactersDataModule + charactersPresentationModule in startKoin,
  and hosts a NavHost(startDestination = CharacterListRoute) calling charactersGraph.
- core:data manifest declares INTERNET (merges into :app) for live API calls.

feature/characters/presentation/src/main/kotlin/com/example/architecture/feature/characters/presentation/di/CharactersPresentationModule.kt

@@ -0,0 +1,10 @@
+package com.example.architecture.feature.characters.presentation.di
+
+import com.example.architecture.feature.characters.presentation.CharacterListViewModel
+import org.koin.core.module.dsl.viewModelOf
+import org.koin.dsl.module
+
+/** Presentation DI for the characters feature. Lives with the (UI-agnostic) ViewModel it provides. */
+val charactersPresentationModule = module {
+    viewModelOf(::CharacterListViewModel)
+}