refactor: Avoid vector for page turn rates list (#1818)

## Summary

Small cleanup to avoid a dynamically allocated static structure for auto
page-turn rate values.

---

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src/activities/reader/EpubReaderActivity.cpp

@@ -10,6 +10,7 @@
 #include <Logging.h>
 #include <esp_system.h>
 
+#include <iterator>
 #include <limits>
 
 #include "CrossPointSettings.h"
@@ -31,7 +32,7 @@ namespace {
 // pagesPerRefresh now comes from SETTINGS.getRefreshFrequency()
 constexpr unsigned long skipChapterMs = 700;
 // pages per minute, first item is 1 to prevent division by zero if accessed
-const std::vector<int> PAGE_TURN_LABELS = {1, 1, 3, 6, 12};
+constexpr int PAGE_TURN_RATES[] = {1, 1, 3, 6, 12};
 
 int clampPercent(int percent) {
   if (percent < 0) {
@@ -469,14 +470,14 @@ void EpubReaderActivity::applyOrientation(const uint8_t orientation) {
 }
 
 void EpubReaderActivity::toggleAutoPageTurn(const uint8_t selectedPageTurnOption) {
-  if (selectedPageTurnOption == 0 || selectedPageTurnOption >= PAGE_TURN_LABELS.size()) {
+  if (selectedPageTurnOption == 0 || selectedPageTurnOption >= std::size(PAGE_TURN_RATES)) {
     automaticPageTurnActive = false;
     return;
   }
 
   lastPageTurnTime = millis();
   // calculates page turn duration by dividing by number of pages
-  pageTurnDuration = (1UL * 60 * 1000) / PAGE_TURN_LABELS[selectedPageTurnOption];
+  pageTurnDuration = (1UL * 60 * 1000) / PAGE_TURN_RATES[selectedPageTurnOption];
   automaticPageTurnActive = true;
 
   const uint8_t statusBarHeight = UITheme::getInstance().getStatusBarHeight();