fix: grid minmax, media polling fallback, content webview layout, swipe timeout

app/src/main/java/top/yeij/hearth/webview/WebViewManager.kt

@@ -26,12 +26,14 @@ class WebViewManager(private val activity: Activity) {
     }
 
     // 创建内容 WebView（webAPP 标签页），仅配置不加载、不挂载（由宿主管理）
+    // 透明背景：webAPP 未声明背景色时透出桌面壁纸，而非默认白底
     // Create a content WebView (webapp tab), configured but not loaded/attached
-    // (lifecycle is managed by the host)
+    // (lifecycle is managed by the host); transparent background so a webapp without
+    // a declared background shows the wallpaper instead of a default white
     @SuppressLint("SetJavaScriptEnabled")
     fun createContentWebView(): WebView {
         val webView = WebView(activity)
-        webView.setBackgroundColor(Color.WHITE)
+        webView.setBackgroundColor(Color.TRANSPARENT)
         configure(webView)
         return webView
     }