style(前台): 列表页去掉表头 emoji、已结束的比赛改成灰色；比赛列表置顶进行中的比赛，排名页先看榜单

- 前台 53 处表头改成纯文字，删掉只剩这一个用途的 utils/renders.ts
- 「已结束」从红色改灰色（比赛列表 / 详情 / 后台 / 首页一起）
- 比赛列表第一页、无筛选时顶部列出进行中和即将开始的比赛
- 内容少的页面页脚贴底，不再悬在半屏
- 排名页两张柱状图挪到最后，第一屏是 Top100、本周进步榜和我的排名

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

apps/web/src/oj/contest/pages/rank.vue

@@ -7,7 +7,6 @@ import { useContestStore } from "oj/store/contest"
 import Pagination from "shared/components/Pagination.vue"
 import { usePagination } from "shared/composables/pagination"
 import { ContestStatus } from "utils/constants"
-import { renderTableTitle } from "utils/renders"
 import type { ContestRank, ProblemRow } from "utils/types"
 import AcAndSubmission from "../components/AcAndSubmission.vue"
 import LineChart from "../components/LineChart.vue"
@@ -45,7 +44,7 @@ const { query } = usePagination({}, { defaultLimit: 50 })
 
 const columns = ref<DataTableColumn<ContestRank>[]>([
   {
-    title: renderTableTitle("编号", "fluent-emoji-flat:input-numbers"),
+    title: "编号",
     key: "id",
     width: 80,
     fixed: "left",
@@ -53,7 +52,7 @@ const columns = ref<DataTableColumn<ContestRank>[]>([
     render: (_, index) => index + (query.page - 1) * query.limit + 1,
   },
   {
-    title: renderTableTitle("用户", "streamline-emojis:smiling-face-with-sunglasses"),
+    title: "用户",
     key: "username",
     width: 120,
     fixed: "left",
@@ -70,7 +69,7 @@ const columns = ref<DataTableColumn<ContestRank>[]>([
       ),
   },
   {
-    title: renderTableTitle("正确数/总提交", "streamline-ultimate-color:color-palette"),
+    title: "正确数/总提交",
     key: "submission",
     width: 140,
     align: "center",