fix: webserver stability, memory leaks, epub underlining, flash screen

Webserver:
- Remove MD5 hash computation from file listings (caused EAGAIN errors)
- Implement JSON batching (2KB) with pacing for file listings
- Simplify sendContentSafe() flow control

Memory:
- Cache QR codes on server start instead of regenerating per render
- Optimize WiFi scan: vector deduplication, 20 network limit, early scanDelete()
- Fix 48KB cover buffer leak when navigating Home -> File Transfer

EPUB Reader:
- Fix errant underlining by flushing partWordBuffer before style changes
- Text before styled inline elements (e.g., <a> with CSS underline) no longer
  incorrectly receives the element's styling

Flash Screen:
- Fix version string buffer overflow (30 -> 50 char limit)
- Use half refresh for cleaner display
- Adjust pre_flash.py timing for half refresh completion

lib/Epub/Epub/parsers/ChapterHtmlSlimParser.cpp

@@ -485,6 +485,9 @@ void XMLCALL ChapterHtmlSlimParser::startElement(void* userData, const XML_Char*
       }
     }
   } else if (matches(name, UNDERLINE_TAGS, NUM_UNDERLINE_TAGS)) {
+    // Flush buffer with CURRENT style before changing effective style
+    self->flushPartWordBuffer();
+
     self->underlineUntilDepth = std::min(self->underlineUntilDepth, self->depth);
     // Push inline style entry for underline tag
     StyleStackEntry entry;
@@ -502,6 +505,9 @@ void XMLCALL ChapterHtmlSlimParser::startElement(void* userData, const XML_Char*
     self->inlineStyleStack.push_back(entry);
     self->updateEffectiveInlineStyle();
   } else if (matches(name, BOLD_TAGS, NUM_BOLD_TAGS)) {
+    // Flush buffer with CURRENT style before changing effective style
+    self->flushPartWordBuffer();
+
     self->boldUntilDepth = std::min(self->boldUntilDepth, self->depth);
     // Push inline style entry for bold tag
     StyleStackEntry entry;
@@ -519,6 +525,9 @@ void XMLCALL ChapterHtmlSlimParser::startElement(void* userData, const XML_Char*
     self->inlineStyleStack.push_back(entry);
     self->updateEffectiveInlineStyle();
   } else if (matches(name, ITALIC_TAGS, NUM_ITALIC_TAGS)) {
+    // Flush buffer with CURRENT style before changing effective style
+    self->flushPartWordBuffer();
+
     self->italicUntilDepth = std::min(self->italicUntilDepth, self->depth);
     // Push inline style entry for italic tag
     StyleStackEntry entry;
@@ -538,6 +547,10 @@ void XMLCALL ChapterHtmlSlimParser::startElement(void* userData, const XML_Char*
   } else if (strcmp(name, "span") == 0 || !isBlockElement) {
     // Handle span and other inline elements for CSS styling
     if (cssStyle.hasFontWeight() || cssStyle.hasFontStyle() || cssStyle.hasTextDecoration()) {
+      // Flush buffer with CURRENT style before changing effective style
+      // This prevents text accumulated before this element from getting the new style
+      self->flushPartWordBuffer();
+
       StyleStackEntry entry;
       entry.depth = self->depth;  // Track depth for matching pop
       if (cssStyle.hasFontWeight()) {
@@ -573,6 +586,33 @@ void XMLCALL ChapterHtmlSlimParser::characterData(void* userData, const XML_Char
     self->lastCharDataOffset = XML_GetCurrentByteIndex(self->xmlParser);
   }
 
+  // If we're inside an <li> but no text block was created yet (direct text without inner <p>),
+  // create a text block and add the list marker now
+  if (self->insideListItem && !self->listItemHasContent) {
+    // Apply left margin for list items
+    CssStyle cssStyle;
+    cssStyle.marginLeft = 24.0f;  // Default indent (~1.5em at 16px base)
+    cssStyle.defined.marginLeft = 1;
+
+    BlockStyle blockStyle = createBlockStyleFromCss(cssStyle);
+    self->startNewTextBlock(static_cast<TextBlock::Style>(self->paragraphAlignment), blockStyle);
+
+    // Add the list marker
+    if (!self->listStack.empty()) {
+      const ListContext& ctx = self->listStack.back();
+      if (ctx.isOrdered) {
+        std::string marker = std::to_string(ctx.counter) + ". ";
+        self->currentTextBlock->addWord(marker, EpdFontFamily::REGULAR);
+      } else {
+        self->currentTextBlock->addWord("\xe2\x80\xa2", EpdFontFamily::REGULAR);
+      }
+    } else {
+      // No list context (orphan li), use bullet as fallback
+      self->currentTextBlock->addWord("\xe2\x80\xa2", EpdFontFamily::REGULAR);
+    }
+    self->listItemHasContent = true;
+  }
+
   // Determine font style from depth-based tracking and CSS effective style
   const bool isBold = self->boldUntilDepth < self->depth || self->effectiveBold;
   const bool isItalic = self->italicUntilDepth < self->depth || self->effectiveItalic;