Fix SSE route dependency and align architecture docs

backend/app/services/rag/__init__.py

@@ -1,11 +1,29 @@
-"""RAG服务模块"""
+"""Initialize the app.services.rag package."""
+# Keep package boundaries explicit so backend imports stay predictable.
 
-from .retriever import Retriever, retrieve_regulations
-from .context_builder import ContextBuilder, build_rag_context
-from .prompt_templates import PromptTemplates, get_prompt_template
 
 __all__ = [
-    "Retriever", "retrieve_regulations",
-    "ContextBuilder", "build_rag_context",
-    "PromptTemplates", "get_prompt_template"
+    "Retriever",
+    "retrieve_regulations",
+    "ContextBuilder",
+    "build_rag_context",
+    "PromptTemplates",
+    "get_prompt_template",
 ]
+
+
+def __getattr__(name: str):
+    """Handle getattr for this module."""
+    if name in {"Retriever", "retrieve_regulations"}:
+        from .retriever import Retriever, retrieve_regulations
+
+        return {"Retriever": Retriever, "retrieve_regulations": retrieve_regulations}[name]
+    if name in {"ContextBuilder", "build_rag_context"}:
+        from .context_builder import ContextBuilder, build_rag_context
+
+        return {"ContextBuilder": ContextBuilder, "build_rag_context": build_rag_context}[name]
+    if name in {"PromptTemplates", "get_prompt_template"}:
+        from .prompt_templates import PromptTemplates, get_prompt_template
+
+        return {"PromptTemplates": PromptTemplates, "get_prompt_template": get_prompt_template}[name]
+    raise AttributeError(name)