feat(gui): 新增主题信息标签，移除 custom_qss 兼容，优化重置按钮

- .ui 新增 ThemeInfoLabel 用于展示主题作者和简介
- ALSettingsWidget 新增 _updateThemeInfo 方法，ComboBox 切换时更新信息
- 移除 _loadQss/_applyQss 模块函数及所有 CUSTOM_QSS 引用
- AppInitializer 移除 _applyQss 导入和回退逻辑
- ConfigProvider/ConfigManager 移除 custom_qss 键
- 纯 QSS 导入通过 ThemeManager 打包为 .altheme 统一管理

src/boot/AppInitializer.py

@@ -15,7 +15,6 @@ from PySide6.QtWidgets import QApplication
 from gui.ALSettingsWidget import (
     _setActiveStyleName,
     _applyTheme,
-    _applyQss,
 )
 from interfaces.ConfigProvider import CfgKey
 from managers.config.ConfigManager import instance as configInstance
@@ -80,7 +79,6 @@ def _initializeAppearance(
     cfg = configInstance()
     saved_style = cfg.get(CfgKey.GLOBAL.APPEARANCE.STYLE, "Fusion")
     saved_theme = cfg.get(CfgKey.GLOBAL.APPEARANCE.THEME, "system")
-    saved_qss = cfg.get(CfgKey.GLOBAL.APPEARANCE.CUSTOM_QSS, "")
     saved_custom_theme = cfg.get(CfgKey.GLOBAL.APPEARANCE.CUSTOM_THEME, "")
     app.setStyle(saved_style)
     _setActiveStyleName(saved_style)
@@ -89,9 +87,7 @@ def _initializeAppearance(
             from managers.theme.ThemeManager import instance as themeInstance
             themeInstance().applyTheme(saved_custom_theme)
         except Exception:
-            _applyQss(saved_qss)
-    else:
-        _applyQss(saved_qss)
+            pass
     _applyTheme(saved_theme)
 
 def initializeApp(