feat(web-admin): plan form package UI keyed by product and package spec

Contract-bound stop products use package options from the contract, arrange-qty
cache/API include packageSpec, and save validates required package selections.

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

web-admin/src/api/pl/index.ts

@@ -901,6 +901,7 @@ export interface ContractProductArrangeQtyDetail {
   contractNo?: string | null
   customerName?: string | null
   productId: string
+  packageSpec?: string | null
   productName?: string | null
   hasFixedQty: boolean
   contractQty?: number | null
@@ -923,6 +924,7 @@ export const planApi = {
   getContractProductArrangeQty: (params: {
     contractId: string
     productId: string
+    packageSpec?: string
     excludePlanId?: string
   }) =>
     request.get<ContractProductArrangeQtyDetail>(
@@ -1165,6 +1167,7 @@ export interface ContractQtyReminderItem {
   customerName?: string
   stopKind: string
   productId: string
+  packageSpec?: string | null
   productName?: string
   model?: string
   unit?: string