feat: timeTableFix 改为构建期组件集成 + git submodule

- 弃用 iframe 嵌入：直接 import 子模块 timeTableFix 的 App.vue 为懒加载路由
  组件，共享 mainPage 构建/依赖(ical.js)/KeepAlive 缓存，无运行期割裂
- git submodule 接入 third_party/timeTableFix（固定到 a49a725），.gitmodules
  使用无凭据 URL；.gitignore 忽略子模块 node_modules
- 删旧 iframe 包装组件 Timetable.vue，移除 app.config 中 timeTableFix 配置
- timetable 模块不再 requiresAlive（构建期已打包，无远程依赖）
- README 更新：项目结构、submodule clone/升级流程、存活校验描述
- 子模块样式隔离（scoped + ttf- 前缀）已在 timeTableFix 侧完成，无泄漏

package-lock.json

@@ -8,6 +8,7 @@
       "name": "mainpage",
       "version": "0.1.0",
       "dependencies": {
+        "ical.js": "^2.1.0",
         "vue": "^3.4.21",
         "vue-i18n": "^9.13.1",
         "vue-router": "^4.3.0"
@@ -986,6 +987,11 @@
         "node": "^8.16.0 || ^10.6.0 || >=11.0.0"
       }
     },
+    "node_modules/ical.js": {
+      "version": "2.2.1",
+      "resolved": "https://registry.npmjs.org/ical.js/-/ical.js-2.2.1.tgz",
+      "integrity": "sha512-yK/UlPbEs316igb/tjRgbFA8ZV75rCsBJp/hWOatpyaPNlgw0dGDmU+FoicOcwX4xXkeXOkYiOmCqNPFpNPkQg=="
+    },
     "node_modules/magic-string": {
       "version": "0.30.21",
       "resolved": "https://registry.npmjs.org/magic-string/-/magic-string-0.30.21.tgz",