积分充值全流程落地：申请审核入账、凭证上传压缩转webp、管理员调账收权

- 新增积分充值申请与审核：商户提交充值申请（凭证图片必填，1元=100积分），
  管理员审核通过后事务内自动入账，幂等键防重复
- 新增通用图片上传组件 ImageUploader：canvas 压缩转 webp、预览、删除，
  后端按魔数校验图片格式并持久化到 data/uploads
- 管理员钱包调整改为按商户维度：移除商户侧调账接口，新增管理员
  平台商户积分调整与钱包流水查看
- 低余额 Webhook 告警配置持久化，充值入账/调账后自动检查推送
- 平台商户操作列移除进入/成员，积分充值页接入真实接口并修复金额单位换算

frontend/src/layouts/MainLayout.tsx

@@ -82,7 +82,10 @@ const adminSections: SidebarSection[] = [
     key: 'funds',
     label: '积分管理',
     icon: <WalletOutlined />,
-    children: [{ key: 'merchant-wallet', label: '积分明细', path: '/merchant-wallet' }],
+    children: [
+      { key: 'merchant-wallet', label: '积分明细', path: '/merchant-wallet' },
+      { key: 'merchant-recharge', label: '积分充值', path: '/merchant-recharge' },
+    ],
   },
   {
     key: 'open-api',
@@ -120,7 +123,10 @@ const merchantSections: SidebarSection[] = [
     key: 'funds',
     label: '积分管理',
     icon: <WalletOutlined />,
-    children: [{ key: 'merchant-wallet', label: '积分明细', path: '/merchant-wallet' }],
+    children: [
+      { key: 'merchant-wallet', label: '积分明细', path: '/merchant-wallet' },
+      { key: 'merchant-recharge', label: '积分充值', path: '/merchant-recharge' },
+    ],
   },
   {
     key: 'staff',
@@ -144,6 +150,7 @@ function getSelectedKey(pathname: string, search: string) {
   if (pathname.startsWith('/merchant-products')) return 'merchant-products'
   if (pathname.startsWith('/merchant-orders')) return 'fulfillment-orders'
   if (pathname.startsWith('/merchant-wallet')) return 'merchant-wallet'
+  if (pathname.startsWith('/merchant-recharge')) return 'merchant-recharge'
   if (pathname.startsWith('/merchant-members')) return 'merchant-members'
   if (pathname.startsWith('/merchant-callbacks')) return 'api-callbacks'
   if (pathname.startsWith('/merchant-api-keys')) return 'api-keys'