fix: Added missing up/down button labels (#935)

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

In some places, button labels are omitted intentionally because the
button has no purpose in the activity. I noticed a few obvious cases,
like Home > File Transfer and Settings > System > Language, where the up
and down button labels were missing. This change fixes those and all
similar instances I could find.

---

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? _**NO**_

src/activities/browser/OpdsBookBrowserActivity.cpp

@@ -189,7 +189,7 @@ void OpdsBookBrowserActivity::render(Activity::RenderLock&&) {
   if (!entries.empty() && entries[selectorIndex].type == OpdsEntryType::BOOK) {
     confirmLabel = tr(STR_DOWNLOAD);
   }
-  const auto labels = mappedInput.mapLabels(tr(STR_BACK), confirmLabel, "", "");
+  const auto labels = mappedInput.mapLabels(tr(STR_BACK), confirmLabel, tr(STR_DIR_UP), tr(STR_DIR_DOWN));
   GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
 
   if (entries.empty()) {

src/activities/network/NetworkModeSelectionActivity.cpp

@@ -78,7 +78,7 @@ void NetworkModeSelectionActivity::render(Activity::RenderLock&&) {
       [](int index) { return std::string(I18N.get(menuDescs[index])); }, [](int index) { return menuIcons[index]; });
 
   // Draw help text at bottom
-  const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), "", "");
+  const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), tr(STR_DIR_UP), tr(STR_DIR_DOWN));
   GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
 
   renderer.displayBuffer();

src/activities/reader/KOReaderSyncActivity.cpp

@@ -282,8 +282,8 @@ void KOReaderSyncActivity::render(Activity::RenderLock&&) {
     }
     renderer.drawText(UI_10_FONT_ID, 20, optionY + optionHeight, tr(STR_UPLOAD_LOCAL), selectedOption != 1);
 
-    // Bottom button hints: show Back and Select
-    const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), "", "");
+    // Bottom button hints
+    const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), tr(STR_DIR_UP), tr(STR_DIR_DOWN));
     GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
     renderer.displayBuffer();
     return;

src/activities/settings/CalibreSettingsActivity.cpp

@@ -142,6 +142,7 @@ void CalibreSettingsActivity::render(Activity::RenderLock&&) {
       },
       true);
 
+
   const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), tr(STR_DIR_UP), tr(STR_DIR_DOWN));
   GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
 

src/activities/settings/KOReaderSettingsActivity.cpp

@@ -168,6 +168,7 @@ void KOReaderSettingsActivity::render(Activity::RenderLock&&) {
       },
       true);
 
+
   const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), tr(STR_DIR_UP), tr(STR_DIR_DOWN));
   GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
 

src/activities/settings/LanguageSelectActivity.cpp

@@ -87,7 +87,7 @@ void LanguageSelectActivity::render(Activity::RenderLock&&) {
   }
 
   // Button hints
-  const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), "", "");
+  const auto labels = mappedInput.mapLabels(tr(STR_BACK), tr(STR_SELECT), tr(STR_DIR_UP), tr(STR_DIR_DOWN));
   GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
 
   renderer.displayBuffer();