Set Dark theme in Settings

Add MyViewModel to keep ThemeSettings state
Use ListItem to display SSIDs in WiFi SSID Policy
Use green color scheme as default color scheme
Add Compose BOM dependency, update dependencies

app/src/main/java/com/bintianqi/owndroid/MyViewModel.kt

@@ -0,0 +1,37 @@
+package com.bintianqi.owndroid
+
+import android.content.Context
+import android.os.Build
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.launch
+
+class MyViewModel: ViewModel() {
+    val theme = MutableStateFlow(ThemeSettings())
+
+    var initialized = false
+    fun initialize(context: Context) {
+        val sharedPrefs = context.getSharedPreferences("data", Context.MODE_PRIVATE)
+        theme.value = ThemeSettings(
+            materialYou = sharedPrefs.getBoolean("material_you", Build.VERSION.SDK_INT >= 31),
+            darkTheme = if(sharedPrefs.contains("dark_theme")) sharedPrefs.getBoolean("dark_theme", false) else null,
+            blackTheme = sharedPrefs.getBoolean("black_theme", false)
+        )
+        viewModelScope.launch {
+            theme.collect {
+                val editor = sharedPrefs.edit()
+                editor.putBoolean("material_you", it.materialYou)
+                if(it.darkTheme == null) editor.remove("dark_theme") else editor.putBoolean("dark_theme", it.darkTheme)
+                editor.putBoolean("black_theme", it.blackTheme)
+                editor.commit()
+            }
+        }
+    }
+}
+
+data class ThemeSettings(
+    val materialYou: Boolean = false,
+    val darkTheme: Boolean? = null,
+    val blackTheme: Boolean = false
+)