Move string helpers out of HomeActivity into StringUtils

src/util/StringUtils.h

@@ -16,4 +16,10 @@ std::string sanitizeFilename(const std::string& name, size_t maxLength = 100);
  */
 bool checkFileExtension(const std::string& fileName, const char* extension);
 
+// UTF-8 safe string truncation - removes one character from the end
+// Returns the new size after removing one UTF-8 character
+size_t utf8RemoveLastChar(std::string& str);
+
+// Truncate string by removing N UTF-8 characters from the end
+void utf8TruncateChars(std::string& str, size_t numChars);
 }  // namespace StringUtils