feat(题目页): 手机上写代码顺手多了：键盘上面多一排常用符号（括号、引号、冒号、缩进…点一下就进去，括号自动配对），代码字号改小、长行折行不再看不见右半截；输入输出说明上下排、例子不再被左边两列标签挤窄；题单里那条不再超出屏幕

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/web/src/oj/problem/detail.vue

@@ -34,6 +34,7 @@ const ProblemContent = defineAsyncComponent(() => import("./components/ProblemCo
 const ProblemDrawer = defineAsyncComponent(() => import("./components/ProblemDrawer.vue"))
 const ResultPane = defineAsyncComponent(() => import("./components/ResultPane.vue"))
 const MobileActionBar = defineAsyncComponent(() => import("./components/MobileActionBar.vue"))
+const SymbolKeys = defineAsyncComponent(() => import("./components/SymbolKeys.vue"))
 
 interface Props {
   problemID: string
@@ -386,6 +387,7 @@ onBeforeUnmount(() => {
       </n-tabs>
       <ProblemDrawer v-model="drawer" />
       <MobileActionBar />
+      <SymbolKeys />
     </div>
   </template>
   <NotFound