Load mentionValues asynchronously (#36739)

Eliminate a few database queries on all issue and pull request pages by
moving mention autocomplete data to async JSON endpoints fetched
on-demand when the user types `@`.

See https://github.com/go-gitea/gitea/pull/36739#issuecomment-3963184858
for the full table of affected pages.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

web_src/js/features/tribute.ts

@@ -1,10 +1,12 @@
 import {emojiKeys, emojiHTML, emojiString} from './emoji.ts';
 import {html, htmlRaw} from '../utils/html.ts';
+import {fetchMentions} from '../utils/match.ts';
 import type {TributeCollection} from 'tributejs';
-import type {MentionValue} from '../types.ts';
+import type {Mention} from '../types.ts';
 
 export async function attachTribute(element: HTMLElement) {
   const {default: Tribute} = await import(/* webpackChunkName: "tribute" */'tributejs');
+  const mentionsUrl = element.closest('[data-mentions-url]')?.getAttribute('data-mentions-url');
 
   const emojiCollection: TributeCollection<string> = { // emojis
     trigger: ':',
@@ -29,8 +31,10 @@ export async function attachTribute(element: HTMLElement) {
     },
   };
 
-  const mentionCollection: TributeCollection<MentionValue> = {
-    values: window.config.mentionValues,
+  const mentionCollection: TributeCollection<Mention> = {
+    values: async (_query: string, cb: (matches: Mention[]) => void) => { // eslint-disable-line @typescript-eslint/no-misused-promises
+      cb(mentionsUrl ? await fetchMentions(mentionsUrl) : []);
+    },
     requireLeadingSpace: true,
     menuItemTemplate: (item) => {
       const fullNameHtml = item.original.fullname && item.original.fullname !== '' ? html`<span class="fullname">${item.original.fullname}</span>` : '';