refactor(admin): unify sortable/draggable/repeater list UI

- Add shared sortable-list.css, SORTABLE_LIST_ATTRS and AksSortHandle
- Migrate schema sortable, selected order, inline/modal repeater, sorter,
  floating buttons, footer tabbar and ticket prereply lists to the shared design
- Split AksField.vue (1885 -> 969 lines) into focused components/helpers
- Remove dead AksArrayTable/AksRepeaterField and move-up/down helpers
- Replace hardcoded colors and --n-* vars with --aksrt-color-* tokens

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

assets/admin/src/components/form/repeater-rows.js

@@ -0,0 +1,65 @@
+/**
+ * repeater / group 行的纯函数：新行默认值、行 ID、listPreview 摘要与预览。
+ * inline 与 list-modal 两种渲染共用。
+ */
+let rowIdCounter = 0
+
+export function createRepeaterRowId() {
+  return `rpt_${Date.now()}_${++rowIdCounter}`
+}
+
+export function createRepeaterRow(fields) {
+  const row = { _id: createRepeaterRowId() }
+  for (const field of (Array.isArray(fields) ? fields : [])) {
+    // UI-only chrome rows (notice / alert) are presentation only.
+    if (field.ui_only) continue
+    if (field.default !== undefined) {
+      row[field.key] = field.default
+    } else if (field.type === 'switch') {
+      row[field.key] = false
+    } else if (field.type === 'checkbox' || field.type === 'repeater') {
+      row[field.key] = []
+    } else {
+      row[field.key] = ''
+    }
+  }
+  return row
+}
+
+/** time/unit 形态的时长摘要：0 视为永久，其余按 day/month 补单位。 */
+function rowDuration(row, cfg) {
+  if (!cfg.descKey) return ''
+  const raw = row[cfg.descKey]
+  if (raw === '' || raw == null) return ''
+  const amount = Number(raw)
+  if (!Number.isFinite(amount)) return String(raw)
+  if (amount <= 0) return '永久'
+  if (!cfg.descUnitKey) return String(raw)
+  const unit = String(row[cfg.descUnitKey] || '')
+  if (unit === 'month') return `${amount} 个月`
+  if (unit === 'day') return `${amount} 天`
+  return String(raw)
+}
+
+/** 收起态标题行上的一行摘要，取自 listPreview 配置。 */
+export function repeaterRowSummary(row, cfg = {}) {
+  if (!row) return ''
+  const title = String(row[cfg.titleKey || 'title'] ?? '').trim()
+  const prefix = String(cfg.prefix || '')
+  if (title === '') return prefix
+  const duration = rowDuration(row, cfg)
+  return duration ? `${prefix}${title} · ${duration}` : `${prefix}${title}`
+}
+
+/** list-modal 卡片预览：图标 / 自定义图标 HTML / 图标类 / 标题 / 描述。 */
+export function repeaterRowPreview(row, cfg = {}) {
+  const read = (key) => String(row?.[key] || '').trim()
+  const desc = read(cfg.descKey || 'desc') || read(cfg.urlKey || 'url')
+  return {
+    icon: read(cfg.iconKey || 'icon'),
+    customIcon: read(cfg.customIconKey || 'custom_icon'),
+    iconClass: read(cfg.iconClassKey || 'icon_class'),
+    title: read(cfg.titleKey || 'title') || '未命名卡片',
+    desc: desc || '暂无描述',
+  }
+}