refactor(后端): 将工资与工作区业务逻辑下沉服务层

将月份状态、资料输出、调整单编排及工作区查询、
CSV 生成移至现有服务层，路由仅绑定参数并返回响应。

保持接口路径、参数、响应模型和权限依赖一致，
补充九项内存库行为回归并同步测试记录。

backend/app/services/payroll_inputs.py

@@ -22,6 +22,20 @@ from app.services.payroll_calculation import latest_input
 from app.services.tplus.workbench import digest
 
 
+def detail(session, business_id):
+    """返回最新核算资料；未准备资料的业务保持空结果。"""
+    record = latest_input(session, business_id)
+    if record is None:
+        return None
+    return {
+        "id": record.id,
+        "version": record.version,
+        "source": record.source_database,
+        "fingerprint": record.fingerprint,
+        "data": record.data_json,
+    }
+
+
 def setup(session, business_id, payload, operator, meta=None):
     with audit_service.audit(
         session,