feat(pl): allocate copy_seq_no on first driver plan share-to-group

Add ensure-copy-seq API and miniprogram clipboard prefix so each plan
gets a tenant-scoped fixed serial on first copy; cover allocation with
unit tests and refresh the backend graph.

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

miniprogram/utils/plDriverPlanCopy.js

@@ -42,7 +42,11 @@ export function buildDriverPlanCopyText(page = {}) {
   const loadStop = stops.find((s) => stopTypeOf(s) === 'load')
   const deliveryStops = stops.filter((s) => stopTypeOf(s) === 'delivery')
 
+  const rawSeq = page?.copySeqNo ?? page?.copy_seq_no
+  const seqText = rawSeq != null && rawSeq !== '' ? String(rawSeq) : DASH
+
   const lines = [
+    `序号：${seqText}`,
     `计划编号：${String(page?.planNo || page?.plan_no || '').trim() || DASH}`,
     `装货方：${loadStop ? customerNameOf(loadStop) : DASH}`
   ]