feat: 人生事件和剧本收藏从 localStorage 切换为真实 API

- 后端：新增 t_event_favorite 表（UNIQUE KEY + MyBatis-Plus Entity）
- 后端：LifeEventController 新增 /favorite/toggle、/favorite/page、/favorite/check 三个真实端点
- 后端：EventFavoriteService 完整 CRUD，含 toggle/分页/批量查询/状态检查
- 后端：删除旧的 favorite-placeholder mock 端点
- 前端：life-event/detail.vue 从 localStorage 假收藏切换为真实 API + localStorage 缓存防闪烁
- 前端：ScriptLibraryView.vue 从 localFavorites 切换为 checkFavoriteScript 真实 API
- 前端：stores/app.js 新增 toggleEventFavorite / checkEventFavorite 方法
- 修复：审核发现的 UNIQUE 约束缺失、未使用 watch 导入、Controller 参数注解遗漏、Controller 委托 Service 构造 Response

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

mini-program/src/services/lifeEvent.js

@@ -64,8 +64,28 @@ export const shareEvent = async (eventData = {}) => {
   return post('/lifeEvent/share-placeholder', eventData)
 }
 
-export const favoriteEvent = async ({ id, favorite }) => {
-  return post('/lifeEvent/favorite-placeholder', { id, favorite })
+/**
+ * 切换人生事件收藏状态（收藏/取消收藏）
+ * @param {string} eventId 事件ID
+ * @returns {Promise<{success: boolean, isFavorited: boolean}>}
+ */
+export const toggleFavoriteEvent = async (eventId) => {
+  const res = await post('/lifeEvent/favorite/toggle', { eventId })
+  return {
+    success: true,
+    isFavorited: res.data?.isFavorited ?? false,
+    favoriteTime: res.data?.favoriteTime ?? null
+  }
+}
+
+/**
+ * 检查人生事件是否已收藏
+ * @param {string} eventId 事件ID
+ * @returns {Promise<boolean>}
+ */
+export const checkFavoriteEvent = async (eventId) => {
+  const res = await get('/lifeEvent/favorite/check', { eventId })
+  return res.data?.isFavorited ?? false
 }
 
 const transformToBackendFormat = (frontendData) => {
@@ -153,7 +173,8 @@ export default {
   assistEventWriting,
   chatAboutEvent,
   shareEvent,
-  favoriteEvent,
+  toggleFavoriteEvent,
+  checkFavoriteEvent,
   transformToFrontendFormat,
   transformListToFrontend
 }