feat(syb): #340 phase 2 — merge main, recompute samples, frontend UI

Merge origin/main (through #345/e7c049d) into feat/340-syb-excluded-products.
Resolved conflicts in sybimport/service.go, handler.go, service_test.go
(kept #342's createdFrom/createdTo AND #340's purchaseType, all combined
with processStage), and took origin/main's syb-products/index.vue as the
base for the new UI work below. Renamed the migration version file from
1789801100000 to 1789801500000 (next free slot after main's highest,
1789801400000) — content unchanged, version comes from the filename.

Backend: sybproductfilter recompute preview now also returns up to 20
sample rows (order code, shopee item id, change direction, matched rule)
alongside the existing counts; execute stays count + audit-log only.

Frontend (feat/340 issue "## 设计证据"/"## 页面", prototype v1):
- SYB 订单商品页: 采购类型 filter (需 PDD 采购 default / 无需 PDD 采购 / 全部),
  处理阶段 gains 无需采购 (pdd_excluded); selecting 退货待确认/已用退货/无需采购
  auto-switches 采购类型 to 全部; pdd_excluded rows are tickable only for
  匹配退货 (never collection/purchase/AI-match/image-search); rows show the
  stage tag plus 规则：<kind> <keyword>; detail drawer shows 采购类型 and rule.
- SYB 过滤规则页: 跳过导入 -> 标记为无需 PDD 采购 wording, 上次同步命中 ->
  上次同步标记, rewritten scope note, admin-only 按当前规则重算 button with
  preview dialog (4 counts + up to 20 samples) -> confirm -> execute.
- SYB 同步记录: 结构/关键词过滤命中 -> 结构/关键词过滤标记 (see #340 point 8;
  the run-level "其中无需采购 N 条" count is derivable client-side from the
  existing char/keyword counts, no backend field added).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NTDbDcwbDw1TSAcE6wfh2F

web/src/api/goauto/syb-product-filters.js

@@ -4,3 +4,5 @@ export function listSybProductFilters(params) { return request({ url: base, meth
 export function createSybProductFilter(data) { return request({ url: base, method: 'post', data }) }
 export function setSybProductFilterEnabled(id, data) { return request({ url: `${base}/${id}/enabled`, method: 'patch', data }) }
 export function deleteSybProductFilter(id) { return request({ url: `${base}/${id}`, method: 'delete' }) }
+export function previewSybProductFilterRecompute() { return request({ url: `${base}/recompute/preview`, method: 'get' }) }
+export function executeSybProductFilterRecompute() { return request({ url: `${base}/recompute/execute`, method: 'post' }) }