fix(sanitizer): normalize non-breaking spaces for WebView compatibility (#2893)

Convert   to   before sanitization and restore after XMLSerializer
serialization. This handles the platform difference where XMLSerializer
produces different representations of non-breaking spaces ( ,  ,
or \u00A0) across different WebView implementations.

apps/readest-app/src/services/transformers/sanitizer.ts

@@ -8,7 +8,7 @@ export const sanitizerTransformer: Transformer = {
     const allowScript = ctx.viewSettings.allowScript;
     if (allowScript) return ctx.content;
 
-    const result = ctx.content;
+    const result = ctx.content.replaceAll(' ', ' ');
 
     const sanitized = DOMPurify.sanitize(result, {
       WHOLE_DOCUMENT: true,
@@ -40,6 +40,7 @@ export const sanitizerTransformer: Transformer = {
 
     const serializer = new XMLSerializer();
     let serialized = serializer.serializeToString(sanitized);
+    serialized = serialized.replaceAll(' ', ' ').replaceAll('\u00A0', ' ');
     serialized = '<?xml version="1.0" encoding="utf-8"?>' + serialized;
     serialized = serialized.replace(/(<head[^>]*>)/i, '\n$1');
     serialized = serialized.replace(/(<\/body>)(<\/html>)/i, '$1\n$2');