chore(fw): replace unsafe calls to strAppend with copyToUnTerminated (#7814)

Co-authored-by: Peter Feerick <5500713+pfeerick@users.noreply.github.com>

radio/src/gui/colorlcd/themes/theme_manager.cpp

@@ -396,7 +396,8 @@ void ThemePersistance::loadDefaultTheme()
   }
 
   for (auto theme : themes) {
-    if (theme->getName().compare(0, SELECTED_THEME_NAME_LEN, g_eeGeneral.selectedTheme) == 0) {
+    if (theme->getName().compare(0, SELECTED_THEME_NAME_LEN,
+                                  stringFromNtString(g_eeGeneral.selectedTheme)) == 0) {
       found = true;
       break;
     }
@@ -469,8 +470,7 @@ bool ThemePersistance::createNewTheme(const std::string& name, ThemeFile& theme)
 void ThemePersistance::setDefaultTheme(int index)
 {
   if (index >= 0 && index < (int)themes.size()) {
-    strAppend(g_eeGeneral.selectedTheme, themes[index]->getName().c_str(),
-              SELECTED_THEME_NAME_LEN);
+    copyToUnTerminated(g_eeGeneral.selectedTheme, themes[index]->getName());
     SET_DIRTY();
     currentTheme = index;
   }

radio/src/storage/yaml/yaml_datastructs_funcs.cpp

@@ -2748,7 +2748,7 @@ static void r_cfs_name(void* user, uint8_t* data, uint32_t bitoffs,
                          const char* val, uint8_t val_len)
 {
   uint16_t idx = getIdx(user);
-  strAppend(g_model.customSwitches[idx].name, val, LEN_SWITCH_NAME);
+  copyToUnTerminated(g_model.customSwitches[idx].name, val);
 }
 
 static const struct YamlNode struct_cfsNameConfig[] = {

radio/src/strhelpers.cpp

@@ -1192,6 +1192,7 @@ char *strAppendSigned(char *dest, int32_t value, uint8_t digits, uint8_t radix)
   return strAppendUnsigned(dest, (uint32_t)value, digits, radix);
 }
 
+// NOTE: 'dest' buffer must be at least 'len + 1' bytes long to allow for nul terminator
 char *strAppend(char *dest, const char *source, int len)
 {
   if (source == nullptr) { *dest = '\0'; return dest; }

radio/src/tests/modelslist_labels.cpp

@@ -99,7 +99,7 @@ class ModelMapFsTest : public ::testing::Test
     // as a compaction optimisation, which would leave this fixture without
     // a "header:" section at all. Giving it a name keeps the fixture
     // realistic and avoids that unrelated edge case.
-    strAppend(model.header.name, filename, LEN_MODEL_NAME);
+    copyToUnTerminated(model.header.name, filename);
     strAppend(model.header.labels, labels, LABELS_LENGTH - 1);
     model.getScreenData(0)->LayoutId = screenLayoutId;
     model.getTopbarData()->zones[0].widgetName = widgetName;