fix: Fix img layout issue / support CSS display:none for elements and images (#1443)

## Summary
- Add CSS `display: none` support to the EPUB rendering pipeline (fixes
#1431)
- Parse `display` property in stylesheets and inline styles, with full
cascade resolution (element, class, element.class, inline)
- Skip hidden elements and all their descendants in
`ChapterHtmlSlimParser`
- Separate display:none check for `<img>` tags (image code path is
independent of the general element handler)
- Flush pending text blocks before placing images to fix layout ordering
(text preceding an image now correctly renders above it)
- Bump CSS cache version to 4 to invalidate stale caches
- Add test EPUB (`test_display_none.epub`) covering class selectors,
element selectors, combined selectors, inline styles, nested hidden
content, hidden images, style priority/override, and realistic use cases

lib/Epub/Epub/parsers/ChapterHtmlSlimParser.cpp

@@ -182,6 +182,24 @@ void XMLCALL ChapterHtmlSlimParser::startElement(void* userData, const XML_Char*
   centeredBlockStyle.textAlignDefined = true;
   centeredBlockStyle.alignment = CssTextAlign::Center;
 
+  // Compute CSS style for this element early so display:none can short-circuit
+  // before tag-specific branches emit any content or metadata.
+  CssStyle cssStyle;
+  if (self->cssParser) {
+    cssStyle = self->cssParser->resolveStyle(name, classAttr);
+    if (!styleAttr.empty()) {
+      CssStyle inlineStyle = CssParser::parseInlineStyle(styleAttr);
+      cssStyle.applyOver(inlineStyle);
+    }
+  }
+
+  // Skip elements with display:none before all fast paths (tables, links, etc.).
+  if (cssStyle.hasDisplay() && cssStyle.display == CssDisplay::None) {
+    self->skipUntilDepth = self->depth;
+    self->depth += 1;
+    return;
+  }
+
   // Special handling for tables/cells: flatten into per-cell paragraphs with a prefixed header.
   if (strcmp(name, "table") == 0) {
     // skip nested tables
@@ -264,6 +282,19 @@ void XMLCALL ChapterHtmlSlimParser::startElement(void* userData, const XML_Char*
         return;
       }
 
+      // Skip image if CSS display:none
+      if (self->cssParser) {
+        CssStyle imgDisplayStyle = self->cssParser->resolveStyle("img", classAttr);
+        if (!styleAttr.empty()) {
+          imgDisplayStyle.applyOver(CssParser::parseInlineStyle(styleAttr));
+        }
+        if (imgDisplayStyle.hasDisplay() && imgDisplayStyle.display == CssDisplay::None) {
+          self->skipUntilDepth = self->depth;
+          self->depth += 1;
+          return;
+        }
+      }
+
       if (!src.empty() && self->imageRendering != 1) {
         LOG_DBG("EHP", "Found image: src=%s", src.c_str());
 
@@ -384,6 +415,15 @@ void XMLCALL ChapterHtmlSlimParser::startElement(void* userData, const XML_Char*
                   LOG_DBG("EHP", "Display size: %dx%d (scale %.2f)", displayWidth, displayHeight, scale);
                 }
 
+                // Flush any pending text block so it appears before the image
+                if (self->partWordBufferIndex > 0) {
+                  self->flushPartWordBuffer();
+                }
+                if (self->currentTextBlock && !self->currentTextBlock->isEmpty()) {
+                  const BlockStyle parentBlockStyle = self->currentTextBlock->getBlockStyle();
+                  self->startNewTextBlock(parentBlockStyle);
+                }
+
                 // Create page for image - only break if image won't fit remaining space
                 if (self->currentPage && !self->currentPage->elements.empty() &&
                     (self->currentPageNextY + displayHeight > self->viewportHeight)) {
@@ -514,18 +554,6 @@ void XMLCALL ChapterHtmlSlimParser::startElement(void* userData, const XML_Char*
     }
   }
 
-  // Compute CSS style for this element
-  CssStyle cssStyle;
-  if (self->cssParser) {
-    // Get combined tag + class styles
-    cssStyle = self->cssParser->resolveStyle(name, classAttr);
-    // Merge inline style (highest priority)
-    if (!styleAttr.empty()) {
-      CssStyle inlineStyle = CssParser::parseInlineStyle(styleAttr);
-      cssStyle.applyOver(inlineStyle);
-    }
-  }
-
   const float emSize = static_cast<float>(self->renderer.getFontAscenderSize(self->fontId));
   const auto userAlignmentBlockStyle = BlockStyle::fromCssStyle(
       cssStyle, emSize, static_cast<CssTextAlign>(self->paragraphAlignment), self->viewportWidth);