Convert frontend code to typescript (#31559)

None of the frontend js/ts files was touched besides these two commands
(edit: no longer true, I touched one file in
61105d0618
because of a deprecation that was not showing before the rename).

`tsc` currently reports 778 errors, so I have disabled it in CI as
planned.

Everything appears to work fine.

web_src/js/features/heatmap.ts

@@ -0,0 +1,42 @@
+import {createApp} from 'vue';
+import ActivityHeatmap from '../components/ActivityHeatmap.vue';
+import {translateMonth, translateDay} from '../utils.ts';
+
+export function initHeatmap() {
+  const el = document.querySelector('#user-heatmap');
+  if (!el) return;
+
+  try {
+    const heatmap = {};
+    for (const {contributions, timestamp} of JSON.parse(el.getAttribute('data-heatmap-data'))) {
+      // Convert to user timezone and sum contributions by date
+      const dateStr = new Date(timestamp * 1000).toDateString();
+      heatmap[dateStr] = (heatmap[dateStr] || 0) + contributions;
+    }
+
+    const values = Object.keys(heatmap).map((v) => {
+      return {date: new Date(v), count: heatmap[v]};
+    });
+
+    // last heatmap tooltip localization attempt https://github.com/go-gitea/gitea/pull/24131/commits/a83761cbbae3c2e3b4bced71e680f44432073ac8
+    const locale = {
+      heatMapLocale: {
+        months: new Array(12).fill().map((_, idx) => translateMonth(idx)),
+        days: new Array(7).fill().map((_, idx) => translateDay(idx)),
+        on: ' - ', // no correct locale support for it, because in many languages the sentence is not "something on someday"
+        more: el.getAttribute('data-locale-more'),
+        less: el.getAttribute('data-locale-less'),
+      },
+      tooltipUnit: 'contributions',
+      textTotalContributions: el.getAttribute('data-locale-total-contributions'),
+      noDataText: el.getAttribute('data-locale-no-contributions'),
+    };
+
+    const View = createApp(ActivityHeatmap, {values, locale});
+    View.mount(el);
+    el.classList.remove('is-loading');
+  } catch (err) {
+    console.error('Heatmap failed to load', err);
+    el.textContent = 'Heatmap failed to load';
+  }
+}