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/api/pl.js

@@ -148,6 +148,8 @@ export const driverPlanApi = {
     return data?.counts && typeof data.counts === 'object' ? data.counts : {}
   },
   get: async (planId) => unwrapData(await db.get(`/transport/driver-plan/${planId}`)),
+  ensureCopySeq: async (planId) =>
+    unwrapData(await db.post(`/transport/driver-plan/${planId}/ensure-copy-seq`, {})),
   saveFeedback: (planId, payload) =>
     db.post(`/transport/driver-plan/${planId}/feedback`, payload),
   saveDriverFeedback: (planId, payload) =>