添加公共工具：联网搜索（DuckDuckGo）和可视化图表（Mermaid）

backend/app/core/__init__.py

@@ -14,6 +14,18 @@ from .human_review import (
     ReviewStatus,
     HumanReview
 )
+from .web_search import (
+    WebSearchTool,
+    SearchResult,
+    get_web_search_tool,
+    web_search
+)
+from .visualization import (
+    VisualizationTool,
+    ChartData,
+    get_visualization_tool,
+    generate_chart
+)
 
 # 为了兼容性，添加 classify_intent 函数
 def classify_intent(user_input: str, context: str = None):
@@ -42,5 +54,13 @@ __all__ = [
     "ReviewManager",
     "InMemoryReviewStore",
     "ReviewStatus",
-    "HumanReview"
+    "HumanReview",
+    "WebSearchTool",
+    "SearchResult",
+    "get_web_search_tool",
+    "web_search",
+    "VisualizationTool",
+    "ChartData",
+    "get_visualization_tool",
+    "generate_chart"
 ]