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/widgets/__init__.py

@@ -9,5 +9,13 @@ from .log_text import LogText
 from .production_id_input import ProductionIdInput
 from .log_handler import GuiTextHandler
 from .delete_progress_window import DeleteProgressWindow
+from .checkbox_treeview import CheckboxTreeview
 
-__all__ = ['FileSelector', 'LogText', 'ProductionIdInput', 'GuiTextHandler', 'DeleteProgressWindow']
+__all__ = [
+    'FileSelector',
+    'LogText',
+    'ProductionIdInput',
+    'GuiTextHandler',
+    'DeleteProgressWindow',
+    'CheckboxTreeview'
+]