feat(ECR-009): Ops-D order filters, plan display prices, refund status

LOOP-RUN-002 sample: admin order multi-filter, membership display
price catalog, read-only refund_status. No real payment or RBAC.

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

docs/BACKEND_DESIGN/BD-2026-009-ops-commerce.md

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+# BD-2026-009 — Ops-D Commerce
+
+Status: Approved  
+**ECR:** ECR-009  
+**Date:** 2026-08-07  
+
+## Backend Change Boundary
+
+### In
+
+- `orders.refund_status` TEXT NOT NULL DEFAULT `none`（`none|pending|refunded|rejected`）  
+- 表 `membership_plan_prices(plan PRIMARY KEY, display_cents INT, updated_at)`  
+- `AdminRepo.ListOrders` 增加 Filter 结构  
+- `AdminRepo` Get/Upsert plan prices + audit `plan_price.upsert`  
+- Handler query 绑定；OpenAPI  
+
+### Out
+
+- 支付渠道 · 退款出账 · Handler 直连 DB  
+
+### Ownership
+
+| Layer | Owner |
+|-------|--------|
+| Repository | AdminRepo |
+| Service | admin.Service |
+| Handler | AdminHandler |
+| UI | admin-h5 Orders / Pricing |
+
+## Architecture Evidence
+
+仍：Handler → Service → Repository；无新外部依赖。