feat: 新增预算后端服务与差旅风险规则库

后端新增预算模型、端点和服务模块，支持预算 CRUD 和余额
查询，清理旧生成规则文件并替换为按严重等级分类的差旅风
险规则库，优化认证权限和报销单访问策略，新增财务规则目
录和演示数据构建脚本，前端预算中心增加对话框交互，完善
审计页面运行时模型和元数据展示，补充单元测试。

server/src/app/api/v1/router.py

@@ -5,6 +5,7 @@ from app.api.v1.endpoints.agent_runs import router as agent_runs_router
 from app.api.v1.endpoints.audit_logs import router as audit_logs_router
 from app.api.v1.endpoints.auth import router as auth_router
 from app.api.v1.endpoints.bootstrap import router as bootstrap_router
+from app.api.v1.endpoints.budgets import router as budgets_router
 from app.api.v1.endpoints.employees import router as employees_router
 from app.api.v1.endpoints.health import router as health_router
 from app.api.v1.endpoints.knowledge import router as knowledge_router
@@ -19,6 +20,7 @@ router = APIRouter()
 router.include_router(health_router, tags=["health"])
 router.include_router(bootstrap_router, tags=["bootstrap"])
 router.include_router(auth_router, tags=["auth"])
+router.include_router(budgets_router, tags=["budgets"])
 router.include_router(agent_assets_router, tags=["agent-assets"])
 router.include_router(agent_runs_router, tags=["agent-runs"])
 router.include_router(audit_logs_router, tags=["audit-logs"])