feat(server): 新增编排器和报销单API端点，扩展智能体对话服务接口

server/src/app/services/agent_conversations.py

@@ -125,6 +125,7 @@ class AgentConversationService:
         user_id: str | None,
         source: str | None = "user_message",
         session_type: str | None = None,
+        prefer_recoverable: bool = False,
     ) -> AgentConversation | None:
         self.prune_expired_conversations()
 
@@ -141,11 +142,36 @@ class AgentConversationService:
         if not normalized_session_type:
             return conversations[0] if conversations else None
 
+        fallback_conversation = None
         for conversation in conversations:
             current_session_type = str((conversation.state_json or {}).get("session_type") or "").strip() or "expense"
-            if current_session_type == normalized_session_type:
+            if current_session_type != normalized_session_type:
+                continue
+            if fallback_conversation is None:
+                fallback_conversation = conversation
+            if not prefer_recoverable or self._is_recoverable_conversation(conversation):
                 return conversation
-        return None
+        return fallback_conversation
+
+    @staticmethod
+    def _is_recoverable_conversation(conversation: AgentConversation) -> bool:
+        if str(conversation.draft_claim_id or "").strip():
+            return True
+
+        state_json = dict(conversation.state_json or {})
+        documents = state_json.get("ocr_documents")
+        if not isinstance(documents, list):
+            return False
+
+        for item in documents:
+            if not isinstance(item, dict):
+                continue
+            preview_url = str(item.get("preview_url") or "").strip()
+            preview_data_url = str(item.get("preview_data_url") or "").strip()
+            preview_kind = str(item.get("preview_kind") or "").strip()
+            if (preview_url or preview_data_url) and preview_kind in {"image", "pdf"}:
+                return True
+        return False
 
     def hydrate_context_json(
         self,