reduce padding around color button

other form elements don't have that padding

src/ui/colorbutton.py

@@ -1,17 +1,18 @@
 import re
 
 from PySide6.QtGui import QColor, QPixmap, QIcon
-from PySide6.QtWidgets import QWidget, QHBoxLayout, QPushButton, QColorDialog, QSizePolicy, QComboBox
+from PySide6.QtWidgets import QWidget, QHBoxLayout, QPushButton, QColorDialog, QSizePolicy, QComboBox, QFrame
 from src.i18n import _
 from src.util.color import to_qcolor
 
 
-class ColorButton(QWidget):
+class ColorButton(QFrame):
     def __init__(self, color: str, parent=None):
         super(ColorButton, self).__init__(parent)
 
         self.setSizePolicy(QSizePolicy(QSizePolicy.Policy.Fixed, QSizePolicy.Policy.Fixed))
         self.layout = QHBoxLayout(self)
+        self.layout.setContentsMargins(0, 0, 0, 0)
 
         colors = {
             # red