feat: add StoreForward `is_server` config

app/src/main/java/com/geeksville/mesh/ui/components/config/StoreForwardConfigItemList.kt

@@ -79,6 +79,15 @@ fun StoreForwardConfigItemList(
                 })
         }
 
+        item {
+            SwitchPreference(
+                title = "Server",
+                checked = storeForwardInput.isServer,
+                enabled = enabled,
+                onCheckedChange = { storeForwardInput = storeForwardInput.copy { isServer = it } })
+        }
+        item { Divider() }
+
         item {
             PreferenceFooter(
                 enabled = storeForwardInput != storeForwardConfig,