refactor(server): steward 意图改用声明式注册表编排

- 新增 steward_intent_registry，IntentDescriptor 统一描述意图的识别关键词、动作步骤构建、字段白名单与副作用集合，替代分散的 if/else
- 新增 steward_intent_bootstrap 注册 expense_application 等意图；新增 steward_query_executors 提供差旅标准查询的无副作用执行与城市/席别标签化输出
- action_contracts/action_executor/graph_planner/intent_agent/model_plan_builder/planner_extraction/fallback 适配注册表，识别与执行分发自动从注册表取数
- 新增 intent_registry/query_executors 测试，更新 intent_agent 测试

server/src/app/services/steward_graph_planner.py

@@ -6,6 +6,7 @@ from typing import Any, TypedDict
 from langgraph.graph import END, START, StateGraph
 
 from app.schemas.steward import StewardPlanRequest, StewardPlanResponse
+from app.services import steward_intent_bootstrap  # noqa: F401  导入即注册全部业务意图
 from app.services.steward_action_contracts import StewardActionPlanBuilder
 from app.services.steward_constants import BUSINESS_CANONICAL_FIELD_ORDER
 from app.services.steward_intent_agent import StewardIntentAgent, StewardIntentAgentResult