feat: Add setting to toggle long-press chapter skip (#341)

## Summary

Adds a new "Long-press Chapter Skip" toggle in Settings to control
whether holding the side buttons skips chapters.

I kept accidentally triggering chapter skips while reading, which caused
me to lose my place in the middle of long chapters.

## Additional Context

* Add any other information that might be helpful for the reviewer
(e.g., performance implications, potential risks,
  specific areas to focus on).

---

### AI Usage

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src/CrossPointSettings.cpp

@@ -14,7 +14,7 @@ CrossPointSettings CrossPointSettings::instance;
 namespace {
 constexpr uint8_t SETTINGS_FILE_VERSION = 1;
 // Increment this when adding new persisted settings fields
-constexpr uint8_t SETTINGS_COUNT = 17;
+constexpr uint8_t SETTINGS_COUNT = 18;
 constexpr char SETTINGS_FILE[] = "/.crosspoint/settings.bin";
 }  // namespace
 
@@ -47,6 +47,7 @@ bool CrossPointSettings::saveToFile() const {
   serialization::writeString(outputFile, std::string(opdsServerUrl));
   serialization::writePod(outputFile, textAntiAliasing);
   serialization::writePod(outputFile, hideBatteryPercentage);
+  serialization::writePod(outputFile, longPressChapterSkip);
   outputFile.close();
 
   Serial.printf("[%lu] [CPS] Settings saved to file\n", millis());
@@ -113,6 +114,8 @@ bool CrossPointSettings::loadFromFile() {
     if (++settingsRead >= fileSettingsCount) break;
     serialization::readPod(inputFile, hideBatteryPercentage);
     if (++settingsRead >= fileSettingsCount) break;
+    serialization::readPod(inputFile, longPressChapterSkip);
+    if (++settingsRead >= fileSettingsCount) break;
   } while (false);
 
   inputFile.close();

src/CrossPointSettings.h

@@ -90,6 +90,8 @@ class CrossPointSettings {
   char opdsServerUrl[128] = "";
   // Hide battery percentage
   uint8_t hideBatteryPercentage = HIDE_NEVER;
+  // Long-press chapter skip on side buttons
+  uint8_t longPressChapterSkip = 1;
 
   ~CrossPointSettings() = default;
 

src/activities/reader/EpubReaderActivity.cpp

@@ -168,7 +168,7 @@ void EpubReaderActivity::loop() {
     return;
   }
 
-  const bool skipChapter = mappedInput.getHeldTime() > skipChapterMs;
+  const bool skipChapter = SETTINGS.longPressChapterSkip && mappedInput.getHeldTime() > skipChapterMs;
 
   if (skipChapter) {
     // We don't want to delete the section mid-render, so grab the semaphore

src/activities/settings/SettingsActivity.cpp

@@ -13,7 +13,7 @@
 
 // Define the static settings list
 namespace {
-constexpr int settingsCount = 19;
+constexpr int settingsCount = 20;
 const SettingInfo settingsList[settingsCount] = {
     // Should match with SLEEP_SCREEN_MODE
     SettingInfo::Enum("Sleep Screen", &CrossPointSettings::sleepScreen, {"Dark", "Light", "Custom", "Cover", "None"}),
@@ -29,6 +29,7 @@ const SettingInfo settingsList[settingsCount] = {
                       {"Bck, Cnfrm, Lft, Rght", "Lft, Rght, Bck, Cnfrm", "Lft, Bck, Cnfrm, Rght"}),
     SettingInfo::Enum("Side Button Layout (reader)", &CrossPointSettings::sideButtonLayout,
                       {"Prev, Next", "Next, Prev"}),
+    SettingInfo::Toggle("Long-press Chapter Skip", &CrossPointSettings::longPressChapterSkip),
     SettingInfo::Enum("Reader Font Family", &CrossPointSettings::fontFamily,
                       {"Bookerly", "Noto Sans", "Open Dyslexic"}),
     SettingInfo::Enum("Reader Font Size", &CrossPointSettings::fontSize, {"Small", "Medium", "Large", "X Large"}),