fix: auto-fix code issues - duplicate imports and unused imports

- 移除函数内部的重复 import re
- 移除函数内部的重复 import csv
- 移除函数内部的重复 import random
- 移除未使用的 urllib.request 导入
- 添加缺失的 time 导入到 ai_manager.py

backend/ai_manager.py

@@ -8,14 +8,14 @@ AI 能力增强模块
 - 预测性分析（趋势预测、异常检测）
 """
 
-import re
-
 import asyncio
 import json
 import os
 import random
+import re
 import sqlite3
 import statistics
+import time
 import uuid
 from collections import defaultdict
 from dataclasses import dataclass
@@ -430,8 +430,6 @@ class AIManager:
             content = result["choices"][0]["message"]["content"]
 
             # 解析 JSON
-            import re
-
             json_match = re.search(r"\[.*?\]", content, re.DOTALL)
             if json_match:
                 try:
@@ -689,8 +687,6 @@ class AIManager:
         self, rag_id: str, query: str, project_entities: list[dict], project_relations: list[dict]
     ) -> RAGQuery:
         """基于知识图谱的 RAG 查询"""
-        import time
-
         start_time = time.time()
 
         rag = self.get_kg_rag(rag_id)

backend/export_manager.py

@@ -275,8 +275,6 @@ class ExportManager:
         Returns:
             CSV 字符串
         """
-        import csv
-
         output = io.StringIO()
 
         # 收集所有可能的属性列

backend/knowledge_reasoner.py

@@ -115,8 +115,6 @@ class KnowledgeReasoner:
 
         content = await self._call_llm(prompt, temperature=0.1)
 
-        import re
-
         json_match = re.search(r"\{{.*?\}}", content, re.DOTALL)
         if json_match:
             try:

backend/plugin_manager.py

@@ -11,7 +11,6 @@ import json
 import os
 import sqlite3
 import time
-import urllib.request
 import uuid
 from dataclasses import dataclass, field
 from datetime import datetime

backend/test_phase8_task8.py

@@ -321,7 +321,6 @@ class TestOpsManager:
 
         try:
             # 记录历史指标数据
-            import random
             base_time = datetime.now() - timedelta(days=30)
             for i in range(30):
                 timestamp = (base_time + timedelta(days=i)).isoformat()

backend/workflow_manager.py

@@ -13,7 +13,6 @@ import asyncio
 import base64
 import hashlib
 import hmac
-import urllib.request
 import json
 import logging
 import uuid