feat(web-admin): add plan draft save UI and drafting follow-status filters

Rename pending tab to 待安排/草稿, default-select drafting, and add 暂存 with saveMode.

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

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

@@ -691,6 +691,7 @@ export interface PlanCreateFullPayload {
   followUserId?: string
   followUserName?: string
   remark?: string
+  saveMode?: 'draft' | 'formal'
   supplierContracts?: PlanContractLink[]
   demanderContracts?: PlanContractLink[]
   load?: PlanLoad