fix: type consistency

include/util/hex_checker.hpp

@@ -2,9 +2,16 @@
 
 #include <string>
 
+/**
+ * Result of transforming 8-bit hex codes to rgba().
+ */
+struct TransformResult {
+  std::string css;
+  bool was_transformed;
+};
+
 /**
  * Reads a CSS file, searches for 8-bit hex codes (#RRGGBBAA),
  * and transforms them into GTK-compatible rgba() syntax.
  */
-
-std::pair<std::string, bool> transform_8bit_to_hex(const std::string& file_path);
+TransformResult transform_8bit_to_hex(const std::string& file_path);