style(ui): 更新按钮文本样式，添加颜色属性

为多个按钮的文本样式表中增加了 `color: #333333` 配置，
以统一界面文字颜色显示效果。涉及的按钮包括：
- 开始安装按钮
- 禁/启用补丁按钮
- 卸载补丁按钮
- 退出程序按钮

source/ui/Ui_install.py

@@ -381,7 +381,7 @@ class Ui_MainWindows(object):
         self.start_install_text.setText("开始安装")
         self.start_install_text.setFont(self.custom_font)
         self.start_install_text.setAlignment(Qt.AlignmentFlag.AlignCenter)
-        self.start_install_text.setStyleSheet("letter-spacing: 1px;")
+        self.start_install_text.setStyleSheet("letter-spacing: 1px; color: #333333;")
 
         # 点击区域透明按钮
         self.start_install_btn = QPushButton(self.button_container)
@@ -415,7 +415,7 @@ class Ui_MainWindows(object):
         self.toggle_patch_text.setText("禁/启用补丁")
         self.toggle_patch_text.setFont(self.custom_font)
         self.toggle_patch_text.setAlignment(Qt.AlignmentFlag.AlignCenter)
-        self.toggle_patch_text.setStyleSheet("letter-spacing: 1px;")
+        self.toggle_patch_text.setStyleSheet("letter-spacing: 1px; color: #333333;")
 
         # 点击区域透明按钮
         self.toggle_patch_btn = QPushButton(self.toggle_patch_container)
@@ -449,7 +449,7 @@ class Ui_MainWindows(object):
         self.uninstall_text.setText("卸载补丁")
         self.uninstall_text.setFont(self.custom_font)
         self.uninstall_text.setAlignment(Qt.AlignmentFlag.AlignCenter)
-        self.uninstall_text.setStyleSheet("letter-spacing: 1px;")
+        self.uninstall_text.setStyleSheet("letter-spacing: 1px; color: #333333;")
 
         # 点击区域透明按钮
         self.uninstall_btn = QPushButton(self.uninstall_container)
@@ -484,7 +484,7 @@ class Ui_MainWindows(object):
         self.exit_text.setText("退出程序")
         self.exit_text.setFont(self.custom_font)
         self.exit_text.setAlignment(Qt.AlignmentFlag.AlignCenter)
-        self.exit_text.setStyleSheet("letter-spacing: 1px;")
+        self.exit_text.setStyleSheet("letter-spacing: 1px; color: #333333;")
         
         # 点击区域透明按钮
         self.exit_btn = QPushButton(self.exit_container)