refactor: extract common tab functionality to BaseTab and add decorators

- Add BaseTab base class for common tab initialization and logging
- Add constants module for shared GUI constants
- Move CheckboxTreeview to separate widget file
- Add admin_only and require_session decorators to utils.py
- Refactor DataExtractionTab and MaterialValidationTab to inherit BaseTab
- Remove duplicate _update_log method from tab classes

Co-Authored-By: Claude (glm-5) <noreply@anthropic.com>

gui/__init__.py

@@ -5,3 +5,27 @@ ERP 自动化工具 - GUI 模块
 """
 
 __version__ = "1.0.0"
+
+# 导出常用模块
+from .base_tab import BaseTab
+from .constants import (
+    WINDOW_SIZE,
+    MIN_WINDOW_SIZE,
+    POLL_INTERVAL_MS,
+    LOG_COLORS,
+    DEFAULT_FONT_FAMILY,
+    DEFAULT_FONT_SIZE,
+)
+from .utils import admin_only, require_session
+
+__all__ = [
+    'BaseTab',
+    'WINDOW_SIZE',
+    'MIN_WINDOW_SIZE',
+    'POLL_INTERVAL_MS',
+    'LOG_COLORS',
+    'DEFAULT_FONT_FAMILY',
+    'DEFAULT_FONT_SIZE',
+    'admin_only',
+    'require_session',
+]