refactor: implement set_dark_theme function for application theming

main.py

@@ -1,6 +1,7 @@
 import sys
 from PySide6.QtWidgets import QApplication
 
+from ui.main_palette import set_dark_theme
 from ui.main_window import MainWindow
 from controllers.main_controller import MainController
 
@@ -8,7 +9,8 @@ from controllers.main_controller import MainController
 
 def main():
     app = QApplication(sys.argv)
-    app.setStyle("Fusion")
+    set_dark_theme(app)
+    # app.setStyle("Fusion")
     window = MainWindow()
     controller = MainController(window)
     controller.load_colors()