feat(server): 新增编排器和报销单API接口，扩展服务编排和报销管理端点

server/src/app/api/v1/endpoints/orchestrator.py

@@ -49,12 +49,14 @@ def get_latest_conversation(
     user_id: Annotated[str, Query(min_length=1, description="当前用户 ID。")],
     db: DbSession,
     session_type: Annotated[str | None, Query(description="会话类型，例如 expense / knowledge。")] = None,
+    prefer_recoverable: Annotated[bool, Query(description="是否优先返回最近一条可恢复的会话。")] = False,
 ) -> ConversationLookupResponse:
     service = AgentConversationService(db)
     conversation = service.get_latest_conversation_for_user(
         user_id=user_id,
         source="user_message",
         session_type=session_type,
+        prefer_recoverable=prefer_recoverable,
     )
     if conversation is None:
         return ConversationLookupResponse(found=False, conversation=None)

server/src/app/api/v1/endpoints/reimbursements.py

@@ -272,6 +272,43 @@ def get_expense_claim_item_attachment_meta(
     return ExpenseClaimAttachmentRead(**payload)
 
 
+@router.get(
+    "/claims/{claim_id}/items/{item_id}/attachment/preview",
+    response_class=FileResponse,
+    summary="读取费用明细附件预览资源",
+    description="优先返回票据预览图；若无单独预览图，则回退到原附件内容。",
+    responses={
+        status.HTTP_404_NOT_FOUND: {
+            "model": ErrorResponse,
+            "description": "报销单、费用明细或附件预览不存在。",
+        },
+    },
+)
+def get_expense_claim_item_attachment_preview(
+    claim_id: str,
+    item_id: str,
+    db: DbSession,
+    current_user: CurrentUser,
+) -> FileResponse:
+    service = ExpenseClaimService(db)
+    try:
+        payload = service.get_claim_item_attachment_preview_content(
+            claim_id=claim_id,
+            item_id=item_id,
+            current_user=current_user,
+        )
+    except LookupError as error:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=str(error)) from error
+    except FileNotFoundError as error:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=str(error)) from error
+
+    if payload is None:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Claim not found")
+
+    file_path, media_type, filename = payload
+    return FileResponse(file_path, media_type=media_type, filename=filename)
+
+
 @router.get(
     "/claims/{claim_id}/items/{item_id}/attachment",
     response_class=FileResponse,