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/dictionary/__init__.py

@@ -0,0 +1,50 @@
+"""
+词典子图 - 完善版
+Dictionary Subgraph Module - Complete
+"""
+
+from .state import (
+    DictionaryState,
+    DictionaryAction,
+    WordEntry,
+    ExtractedTerm
+)
+from .graph import build_dictionary_subgraph
+from .nodes import (
+    parse_intent,
+    query_word,
+    translate_text,
+    extract_terms,
+    get_daily_word,
+    lookup_word_book,
+    add_to_word_book,
+    format_result,
+    should_continue
+)
+from .api_client import dictionary_api, DictionaryAPIClient
+
+__all__ = [
+    # State
+    "DictionaryState",
+    "DictionaryAction",
+    "WordEntry",
+    "ExtractedTerm",
+    
+    # Graph
+    "build_dictionary_subgraph",
+    
+    # Nodes
+    "parse_intent",
+    "query_word",
+    "translate_text",
+    "extract_terms",
+    "get_daily_word",
+    "lookup_word_book",
+    "add_to_word_book",
+    "format_result",
+    "should_continue",
+    
+    # API
+    "dictionary_api",
+    "DictionaryAPIClient"
+]