fix: improve dark mode loading by setting WebView invisible in XML and increasing delay

- Set WebView visibility to invisible in XML layout to prevent initial white flash
- Increase delay from 100ms to 300ms to ensure theme JavaScript executes properly
- This eliminates the white screen gap during page load in dark mode

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: graycreate

app/src/main/java/me/ghui/v2er/module/vshare/VshareWebActivity.java

@@ -188,7 +188,7 @@ public void run() {
                         mWebView.setVisibility(View.VISIBLE);
                         hideLoading();
                     }
-                }, 100);
+                }, 300);
             }
         });
     }

app/src/main/res/layout/activity_vshare_web.xml

@@ -6,6 +6,7 @@
 
     <WebView
         android:id="@+id/webview"
+        android:visibility="invisible"
         android:layout_width="match_parent"
         android:layout_height="match_parent" />