Replace StateViewModel with explicit backing fields (#3763)

Assisted-by: Claude:claude-opus-5

core/viewmodel/build.gradle.kts

@@ -1,14 +0,0 @@
-plugins {
-    alias(mihonx.plugins.android.library)
-    alias(mihonx.plugins.spotless)
-
-    alias(libs.plugins.kotlin.serialization)
-}
-
-android {
-    namespace = "mihon.core.viewmodel"
-}
-
-dependencies {
-    implementation(libs.androidx.lifecycle.viewmodel)
-}

core/viewmodel/src/main/AndroidManifest.xml

@@ -1,2 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<manifest />

core/viewmodel/src/main/kotlin/mihon/core/viewmodel/StateViewModel.kt

@@ -1,11 +0,0 @@
-package mihon.core.viewmodel
-
-import androidx.lifecycle.ViewModel
-import kotlinx.coroutines.flow.MutableStateFlow
-import kotlinx.coroutines.flow.StateFlow
-import kotlinx.coroutines.flow.asStateFlow
-
-abstract class StateViewModel<S>(initialState: S) : ViewModel() {
-    protected val mutableState: MutableStateFlow<S> = MutableStateFlow(initialState)
-    val state: StateFlow<S> = mutableState.asStateFlow()
-}