task-112(任务与重复分析中心): 实现店铺数据任务批量选择

新增 shop-data-selection.ts：店铺数据结果 result_id 选择集(字符串兼容)的
纯切换/批量操作。

TDD: task-112.test.ts 8 用例先 RED 后 GREEN。

admin-frontend-vue/src/pages/tasks/shop-data-selection.ts

@@ -0,0 +1,33 @@
+/** 店铺数据结果批量选择（任务 112）：result_id 选择集(字符串兼容)的纯操作。 */
+
+export function createShopDataSelection(): Set<string> {
+  return new Set<string>()
+}
+
+function validKey(key: string): boolean {
+  return typeof key === 'string' && key.length > 0
+}
+
+export function toggleShopDataSelection(selection: Set<string>, resultId: string): Set<string> {
+  const next = new Set(selection)
+  if (!validKey(resultId)) return next
+  if (next.has(resultId)) next.delete(resultId)
+  else next.add(resultId)
+  return next
+}
+
+export function addShopDataSelection(selection: Set<string>, resultIds: readonly string[]): Set<string> {
+  const next = new Set(selection)
+  for (const id of resultIds) if (validKey(id)) next.add(id)
+  return next
+}
+
+export function removeShopDataSelection(selection: Set<string>, resultIds: readonly string[]): Set<string> {
+  const next = new Set(selection)
+  for (const id of resultIds) next.delete(id)
+  return next
+}
+
+export function countShopDataSelection(selection: Set<string>): number {
+  return selection.size
+}