Fix SSE route dependency and align architecture docs

backend/app/services/llm/__init__.py

@@ -1,14 +1,36 @@
-"""LLM服务模块"""
+"""Initialize the app.services.llm package."""
 
-from .llm_factory import LLMFactory, get_llm_client
-from .base_client import BaseLLMClient, LLMResponse, LLMConfig, LLMProvider
+from .base_client import BaseLLMClient, LLMConfig, LLMProvider, LLMResponse
 from .deepseek_client import DeepSeekClient
+from .llm_factory import LLMFactory, get_llm_client
 from .qwen_client import QwenClient, QwenVLClient
-from .document_summarizer import DocumentSummarizer, summarize_document, DocumentSummary
+# Keep package boundaries explicit so backend imports stay predictable.
+
 
 __all__ = [
-    "LLMFactory", "get_llm_client",
-    "BaseLLMClient", "LLMResponse", "LLMConfig", "LLMProvider",
-    "DeepSeekClient", "QwenClient", "QwenVLClient",
-    "DocumentSummarizer", "summarize_document", "DocumentSummary"
+    "LLMFactory",
+    "get_llm_client",
+    "BaseLLMClient",
+    "LLMResponse",
+    "LLMConfig",
+    "LLMProvider",
+    "DeepSeekClient",
+    "QwenClient",
+    "QwenVLClient",
+    "DocumentSummarizer",
+    "summarize_document",
+    "DocumentSummary",
 ]
+
+
+def __getattr__(name: str):
+    """Handle getattr for this module."""
+    if name in {"DocumentSummarizer", "summarize_document", "DocumentSummary"}:
+        from .document_summarizer import DocumentSummarizer, DocumentSummary, summarize_document
+
+        return {
+            "DocumentSummarizer": DocumentSummarizer,
+            "summarize_document": summarize_document,
+            "DocumentSummary": DocumentSummary,
+        }[name]
+    raise AttributeError(name)