Fix SSE route dependency and align architecture docs

backend/app/domain/conversation/__init__.py

@@ -0,0 +1,15 @@
+"""Initialize the app.domain.conversation package."""
+
+from .models import AnswerResult, AnswerSource, ConversationMessage, ConversationSession
+from .ports import AnswerGenerator, ConversationStore
+# Keep package boundaries explicit so backend imports stay predictable.
+
+
+__all__ = [
+    "AnswerGenerator",
+    "AnswerResult",
+    "AnswerSource",
+    "ConversationMessage",
+    "ConversationSession",
+    "ConversationStore",
+]