feat(bx): invoice upload/delete APIs and wallet summary

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/api/bx/__init__.py

@@ -1,7 +1,7 @@
 """报销（bx）API 路由聚合 — REST 风格，协议对齐 bx 原系统。"""
 from fastapi import APIRouter
 
-from app.api.bx import advance, attachment, expense_item, payment, reimburse, workflow
+from app.api.bx import advance, attachment, expense_item, invoice, payment, reimburse, workflow
 from app.schemas.bx.common import ApiResponse
 
 bx_router = APIRouter(tags=["报销管理"])
@@ -11,6 +11,7 @@ bx_router.include_router(advance.router)
 bx_router.include_router(attachment.router)
 bx_router.include_router(reimburse.router)
 bx_router.include_router(payment.router)
+bx_router.include_router(invoice.router)
 
 
 @bx_router.get("/bx/health", response_model=ApiResponse[dict])