feat(distribution): 分站可下调收号比例且不超过主站上限

让分销站能按自身能力下调收号比例扩大利润，同时把主站回收比例作为硬边界，避免分站把比例加得比主站更高。

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

frontend/src/stores/distributionSite.ts

@@ -27,6 +27,7 @@ export interface DistributionSiteInfo {
   banners_json?: string
   announcements_json?: string
   footer_info_json?: string
+  receive_ratio_delta?: number
 }
 
 /**
@@ -72,6 +73,7 @@ export const useDistributionSiteStore = defineStore('distributionSite', {
       banners: [] as DistributionBanner[],
       announcements: [] as string[],
       footerInfo: null as DistributionFooterInfo | null,
+      receiveRatioDelta: 0,
       initialized: false,
     }
   },
@@ -175,6 +177,8 @@ export const useDistributionSiteStore = defineStore('distributionSite', {
             this.footerInfo = null
           }
 
+          this.receiveRatioDelta = Math.max(0, Number(info.receive_ratio_delta || 0))
+
           sessionStorage.setItem('hfb_site_code', this.siteCode)
           sessionStorage.setItem('hfb_site_name', this.siteName)
 
@@ -212,6 +216,7 @@ export const useDistributionSiteStore = defineStore('distributionSite', {
       this.banners = []
       this.announcements = []
       this.footerInfo = null
+      this.receiveRatioDelta = 0
       sessionStorage.removeItem('hfb_site_code')
       sessionStorage.removeItem('hfb_site_name')
       localStorage.removeItem('hfb_site_code')