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/contact/__init__.py

@@ -0,0 +1,47 @@
+"""
+通讯录子图
+Contact Subgraph Module
+"""
+
+from .state import (
+    ContactState,
+    Contact,
+    Email,
+    ContactAction
+)
+from .graph import build_contact_subgraph
+from .nodes import (
+    parse_intent,
+    list_contacts,
+    add_contact,
+    list_emails,
+    generate_email_draft,
+    human_review,
+    send_email,
+    sniff_contacts,
+    format_result,
+    should_continue
+)
+
+__all__ = [
+    # State
+    "ContactState",
+    "Contact",
+    "Email",
+    "ContactAction",
+    
+    # Graph
+    "build_contact_subgraph",
+    
+    # Nodes
+    "parse_intent",
+    "list_contacts",
+    "add_contact",
+    "list_emails",
+    "generate_email_draft",
+    "human_review",
+    "send_email",
+    "sniff_contacts",
+    "format_result",
+    "should_continue"
+]