Use desktop User-Agent by default

Since WebP resamples have smaller file size.

app/src/main/kotlin/com/hippo/ehviewer/Settings.kt

@@ -165,7 +165,7 @@ object Settings : DataStorePreferences(null) {
     var downloadOriginImage by boolPref("download_origin_image", false)
     var saveAsCbz by boolPref("save_as_cbz", false)
     var archiveMetadata by boolPref("archive_metadata", true)
-    var desktopSite by boolPref("desktop_site", false)
+    var desktopSite by boolPref("desktop_site", true)
     var recentFavCat by intPref("recent_fav_cat", FavListUrlBuilder.FAV_CAT_LOCAL)
     var defaultFavSlot by intPref("default_favorite_slot", -2)
     var securityDelay by intPref("require_unlock_delay", 0)