fix: hide WebView until theme is applied to prevent white flash

Changed approach to completely eliminate white flash in dark mode:
- Set WebView to INVISIBLE before loading
- Apply theme via JavaScript when page finishes loading
- Show WebView after 100ms delay to ensure JS executes
- Hide loading indicator when WebView becomes visible

This ensures users only see the WebView after the correct theme
has been fully applied, completely eliminating the white flash
that occurred during page load in dark mode.

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

Co-Authored-By: Claude <noreply@anthropic.com>

Author: graycreate

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

@@ -105,6 +105,9 @@ protected void init() {
 
     @SuppressLint("SetJavaScriptEnabled")
     private void setupWebView() {
+        // Hide WebView until page is fully loaded with correct theme
+        mWebView.setVisibility(View.INVISIBLE);
+
         // Set WebView background color to match theme before loading
         boolean isDarkMode = DarkModelUtils.isDarkMode();
         if (isDarkMode) {
@@ -170,14 +173,22 @@ public void onPageStarted(WebView view, String url, Bitmap favicon) {
             @Override
             public void onPageFinished(WebView view, String url) {
                 super.onPageFinished(view, url);
-                hideLoading();
 
                 // Inject CSS to ensure proper theme is applied
                 String theme = DarkModelUtils.isDarkMode() ? "dark" : "light";
                 String js = "javascript:(function() { " +
                         "document.documentElement.setAttribute('data-theme', '" + theme + "'); " +
                         "})()";
                 mWebView.loadUrl(js);
+
+                // Show WebView after theme is applied (small delay to ensure JS executes)
+                mWebView.postDelayed(new Runnable() {
+                    @Override
+                    public void run() {
+                        mWebView.setVisibility(View.VISIBLE);
+                        hideLoading();
+                    }
+                }, 100);
             }
         });
     }