Fix date rendering by adding <gitea-absolute-date> (#29725)

Alternative to: https://github.com/go-gitea/gitea/pull/29698
Fixes: https://github.com/go-gitea/gitea/issues/29034

<img width="278" alt="image"
src="12ecd967-2723-410d-8a28-a1b0f41b7bba">

It also fixes a secondary issue that we were showing timestamp tooltips
over date, which makes no sense, so these are now gone as well:

<img width="284" alt="image"
src="a70432f3-97b6-41e6-b202-b53b76924a66">

(cherry picked from commit 857243bed7f9dccdc597c2941df41e821781cb0f)

web_src/js/webcomponents/GiteaAbsoluteDate.js

@@ -0,0 +1,40 @@
+window.customElements.define('gitea-absolute-date', class extends HTMLElement {
+  static observedAttributes = ['date', 'year', 'month', 'weekday', 'day'];
+
+  update = () => {
+    const year = this.getAttribute('year') ?? '';
+    const month = this.getAttribute('month') ?? '';
+    const weekday = this.getAttribute('weekday') ?? '';
+    const day = this.getAttribute('day') ?? '';
+    const lang = this.closest('[lang]')?.getAttribute('lang') ||
+      this.ownerDocument.documentElement.getAttribute('lang') ||
+      '';
+
+    // only extract the `yyyy-mm-dd` part. When converting to Date, it will become midnight UTC and when rendered
+    // as localized date, will have a offset towards UTC, which we remove to shift the timestamp to midnight in the
+    // localized date. We should eventually use `Temporal.PlainDate` which will make the correction unnecessary.
+    // - https://stackoverflow.com/a/14569783/808699
+    // - https://tc39.es/proposal-temporal/docs/plaindate.html
+    const date = new Date(this.getAttribute('date').substring(0, 10));
+    const correctedDate = new Date(date.getTime() - date.getTimezoneOffset() * -60000);
+
+    if (!this.shadowRoot) this.attachShadow({mode: 'open'});
+    this.shadowRoot.textContent = correctedDate.toLocaleString(lang ?? [], {
+      ...(year && {year}),
+      ...(month && {month}),
+      ...(weekday && {weekday}),
+      ...(day && {day}),
+    });
+  };
+
+  attributeChangedCallback(_name, oldValue, newValue) {
+    if (!this.initialized || oldValue === newValue) return;
+    this.update();
+  }
+
+  connectedCallback() {
+    this.initialized = false;
+    this.update();
+    this.initialized = true;
+  }
+});

web_src/js/webcomponents/webcomponents.js

@@ -3,3 +3,4 @@ import './polyfill.js';
 
 import '@github/relative-time-element';
 import './GiteaOriginUrl.js';
+import './GiteaAbsoluteDate.js';