feat: Add Settings for toggling CSS on or off (#717)

Closes #712 

## Summary

**What is the goal of this PR?** 

- To add new settings for toggling on/off embedded CSS styles in the
reader. This gives more control and customization to the user over how
the ereader experience looks.

**What changes are included?**

- Added new "Embedded Style" option to the Reader settings
- Added new "Book's Style" option for "Paragraph Alignment"
- User's selected "Paragraph Alignment" will take precedence and
override the embedded CSS `text-align` property, _unless_ the user has
"Book's Style" set as their "Paragraph Alignment"

## Additional Context

![IMG_6336](https://github.com/user-attachments/assets/dff619ef-986d-465e-b352-73a76baae334)


https://github.com/user-attachments/assets/9e404b13-c7e0-41c7-9406-4715f389166a


Addresses feedback from the community about the new CSS feature:
https://github.com/crosspoint-reader/crosspoint-reader/pull/700

---

### AI Usage

While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.

Did you use AI tools to help write this code? _**YES**_, Claude Code

src/CrossPointSettings.cpp

@@ -22,7 +22,7 @@ void readAndValidate(FsFile& file, uint8_t& member, const uint8_t maxValue) {
 namespace {
 constexpr uint8_t SETTINGS_FILE_VERSION = 1;
 // Increment this when adding new persisted settings fields
-constexpr uint8_t SETTINGS_COUNT = 29;
+constexpr uint8_t SETTINGS_COUNT = 30;
 constexpr char SETTINGS_FILE[] = "/.crosspoint/settings.bin";
 
 // Validate front button mapping to ensure each hardware button is unique.
@@ -117,6 +117,7 @@ bool CrossPointSettings::saveToFile() const {
   serialization::writePod(outputFile, frontButtonLeft);
   serialization::writePod(outputFile, frontButtonRight);
   serialization::writePod(outputFile, fadingFix);
+  serialization::writePod(outputFile, embeddedStyle);
   // New fields added at end for backward compatibility
   outputFile.close();
 
@@ -220,6 +221,8 @@ bool CrossPointSettings::loadFromFile() {
     if (++settingsRead >= fileSettingsCount) break;
     serialization::readPod(inputFile, fadingFix);
     if (++settingsRead >= fileSettingsCount) break;
+    serialization::readPod(inputFile, embeddedStyle);
+    if (++settingsRead >= fileSettingsCount) break;
     // New fields added at end for backward compatibility
   } while (false);
 

src/CrossPointSettings.h

@@ -86,6 +86,7 @@ class CrossPointSettings {
     LEFT_ALIGN = 1,
     CENTER_ALIGN = 2,
     RIGHT_ALIGN = 3,
+    BOOK_STYLE = 4,
     PARAGRAPH_ALIGNMENT_COUNT
   };
 
@@ -168,6 +169,8 @@ class CrossPointSettings {
   uint8_t uiTheme = LYRA;
   // Sunlight fading compensation
   uint8_t fadingFix = 0;
+  // Use book's embedded CSS styles for EPUB rendering (1 = enabled, 0 = disabled)
+  uint8_t embeddedStyle = 1;
 
   ~CrossPointSettings() = default;
 

src/activities/reader/EpubReaderActivity.cpp

@@ -575,14 +575,14 @@ void EpubReaderActivity::renderScreen() {
 
     if (!section->loadSectionFile(SETTINGS.getReaderFontId(), SETTINGS.getReaderLineCompression(),
                                   SETTINGS.extraParagraphSpacing, SETTINGS.paragraphAlignment, viewportWidth,
-                                  viewportHeight, SETTINGS.hyphenationEnabled)) {
+                                  viewportHeight, SETTINGS.hyphenationEnabled, SETTINGS.embeddedStyle)) {
       Serial.printf("[%lu] [ERS] Cache not found, building...\n", millis());
 
       const auto popupFn = [this]() { GUI.drawPopup(renderer, "Indexing..."); };
 
       if (!section->createSectionFile(SETTINGS.getReaderFontId(), SETTINGS.getReaderLineCompression(),
                                       SETTINGS.extraParagraphSpacing, SETTINGS.paragraphAlignment, viewportWidth,
-                                      viewportHeight, SETTINGS.hyphenationEnabled, popupFn)) {
+                                      viewportHeight, SETTINGS.hyphenationEnabled, SETTINGS.embeddedStyle, popupFn)) {
         Serial.printf("[%lu] [ERS] Failed to persist page data to SD\n", millis());
         section.reset();
         return;

src/activities/settings/SettingsActivity.cpp

@@ -35,14 +35,15 @@ const SettingInfo displaySettings[displaySettingsCount] = {
     SettingInfo::Toggle("Sunlight Fading Fix", &CrossPointSettings::fadingFix),
 };
 
-constexpr int readerSettingsCount = 9;
+constexpr int readerSettingsCount = 10;
 const SettingInfo readerSettings[readerSettingsCount] = {
     SettingInfo::Enum("Font Family", &CrossPointSettings::fontFamily, {"Bookerly", "Noto Sans", "Open Dyslexic"}),
     SettingInfo::Enum("Font Size", &CrossPointSettings::fontSize, {"Small", "Medium", "Large", "X Large"}),
     SettingInfo::Enum("Line Spacing", &CrossPointSettings::lineSpacing, {"Tight", "Normal", "Wide"}),
     SettingInfo::Value("Screen Margin", &CrossPointSettings::screenMargin, {5, 40, 5}),
     SettingInfo::Enum("Paragraph Alignment", &CrossPointSettings::paragraphAlignment,
-                      {"Justify", "Left", "Center", "Right"}),
+                      {"Justify", "Left", "Center", "Right", "Book's Style"}),
+    SettingInfo::Toggle("Embedded Style", &CrossPointSettings::embeddedStyle),
     SettingInfo::Toggle("Hyphenation", &CrossPointSettings::hyphenationEnabled),
     SettingInfo::Enum("Reading Orientation", &CrossPointSettings::orientation,
                       {"Portrait", "Landscape CW", "Inverted", "Landscape CCW"}),