feat: implement unified logging system for GUI components

Add centralized logging mechanism that simultaneously outputs to console
and GUI log components, improving code maintainability and consistency.

Changes:
- Add gui/log_config.py for centralized logging configuration
- Add gui/widgets/log_handler.py as bridge between logging and LogText
- Integrate unified logging into DataExtractionTab and MaterialValidationTab
- Initialize logging system in MainWindow on startup
- Improve error messages in material_status_validator for empty results
- Add documentation for logging mechanism and refactoring

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

utils/material_status_validator.py

@@ -466,6 +466,15 @@ class MaterialStatusValidator:
             dao = DiscreteMaterialPlanDAO()
             material_records = dao.query_by_source_numbers(source_numbers)
             self._print(f"[INFO] 获取到 {len(material_records)} 条记录")
+
+            # 如果没有找到物料记录，给出友好提示
+            if not material_records:
+                self._print("\n[ERROR] 校验失败：未找到物料记录")
+                self._print("[ERROR] 可能原因：")
+                self._print("[ERROR]   1. 这些生产订单的物料数据还没有提取到数据库")
+                self._print("[ERROR]   2. 请先运行【正式备料计划数据提取】工具")
+                self._print("[ERROR]   3. 提取时勾选【持久化到数据库】选项")
+                self._print("[ERROR]   4. 将这 10 个 ProductionID 的物料数据保存到 DiscreteMaterialPlanData 表")
         else:
             raise ValueError("必须指定 full_table=True 或提供 production_id_file 参数")