feat: 完善词典子图，添加API调用和前端格式化工具

- 完善词典子图：添加生词本功能
- 创建API调用工具：dictionary_api
- 添加前端格式化展示工具：result_formatter.py
- 创建通讯录和资讯子图的基本结构
- 更新主图状态结构，添加MainGraphState
- 添加subgraph_builder.py用于子图集成

backend/app/agent_subgraphs/news_analysis/graph.py

@@ -0,0 +1,63 @@
+"""
+资讯子图构建器
+News Analysis Subgraph Builder
+"""
+
+from langgraph.graph import StateGraph, START, END
+
+from .state import NewsAnalysisState
+from .nodes import (
+    parse_intent,
+    query_news,
+    analyze_url,
+    extract_keywords,
+    generate_report,
+    format_result,
+    should_continue
+)
+
+
+def build_news_analysis_subgraph() -> StateGraph:
+    """
+    构建资讯子图
+    
+    Returns:
+        配置好的 StateGraph
+    """
+    # 创建图
+    graph = StateGraph(NewsAnalysisState)
+    
+    # 添加节点
+    graph.add_node("parse_intent", parse_intent)
+    graph.add_node("query_news", query_news)
+    graph.add_node("analyze_url", analyze_url)
+    graph.add_node("extract_keywords", extract_keywords)
+    graph.add_node("generate_report", generate_report)
+    graph.add_node("format_result", format_result)
+    
+    # 添加边
+    # 从START开始
+    graph.add_edge(START, "parse_intent")
+    
+    # 从parse_intent根据条件路由
+    graph.add_conditional_edges(
+        "parse_intent",
+        should_continue,
+        {
+            "query_news": "query_news",
+            "analyze_url": "analyze_url",
+            "extract_keywords": "extract_keywords",
+            "generate_report": "generate_report",
+        }
+    )
+    
+    # 从各个操作节点到format_result
+    graph.add_edge("query_news", "format_result")
+    graph.add_edge("analyze_url", "format_result")
+    graph.add_edge("extract_keywords", "format_result")
+    graph.add_edge("generate_report", "format_result")
+    
+    # 最终到END
+    graph.add_edge("format_result", END)
+    
+    return graph