refactor: rename Chinese-named Python files to English

Rename utility files to use English names for better cross-platform compatibility:
- utils/离散备料计划维护数据提取.py → utils/discrete_material_plan_extractor.py
- utils/离散备料计划维护数据清理.py → utils/discrete_material_plan_cleaner.py

Update all import statements across the codebase and documentation references.

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

docs/MAIN_CLEAN_FLOW.md

@@ -110,7 +110,7 @@ flowchart TB
     style C fill:#fff4e1
 ```
 
-**代码位置**: `utils/离散备料计划维护数据清理.py:292-304`
+**代码位置**: `utils/discrete_material_plan_cleaner.py:292-304`
 
 | 模块 | 功能 | 文件 |
 |------|------|------|
@@ -162,7 +162,7 @@ flowchart TB
     style F fill:#ffe1e1
 ```
 
-**代码位置**: `utils/离散备料计划维护数据清理.py:263-290`
+**代码位置**: `utils/discrete_material_plan_cleaner.py:263-290`
 
 ---
 
@@ -179,7 +179,7 @@ flowchart LR
     style D fill:#fff4e1
 ```
 
-**代码位置**: `utils/离散备料计划维护数据清理.py:41-59`
+**代码位置**: `utils/discrete_material_plan_cleaner.py:41-59`
 
 | 函数 | 功能 | 数据库表 |
 |------|------|----------|
@@ -210,7 +210,7 @@ flowchart TB
     style CheckStatus fill:#fff4e1
 ```
 
-**代码位置**: `utils/离散备料计划维护数据清理.py:61-167`
+**代码位置**: `utils/discrete_material_plan_cleaner.py:61-167`
 
 ---
 
@@ -249,7 +249,7 @@ flowchart TB
     style Done fill:#e1f5ff
 ```
 
-**代码位置**: `utils/离散备料计划维护数据清理.py:169-261`
+**代码位置**: `utils/discrete_material_plan_cleaner.py:169-261`
 
 ---
 
@@ -311,7 +311,7 @@ classDiagram
 
 ```mermaid
 graph TD
-    A[main_clean.py] --> B[utils/离散备料计划维护数据清理.py]
+    A[main_clean.py] --> B[utils/discrete_material_plan_cleaner.py]
     B --> C[utils/auth.py]
     B --> D[db/production_order_query.py]
     B --> E[db/materials_to_delete.py]

docs/progress_callback_mechanism.md

@@ -142,7 +142,7 @@ pie title 各阶段权重分布
 ### 1. 后台任务：报告进度
 
 ```python
-# utils/离散备料计划维护数据提取.py
+# utils/discrete_material_plan_extractor.py
 
 def _report_progress(self, stage: str, current: int, total: int, message: str, **detail):
     """