refactor: replace Fomantic search module with first-party code (#37443)

- Replace fomantic `search` code with minimal first-party code
- Added a small fix to vertically align search box and search button
- Manually tested all search forms.
- Add `errorName` helper, similar to `errorMessage`.

Signed-off-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.7) <noreply@anthropic.com>

templates/admin/badge/users.tmpl

@@ -4,8 +4,8 @@
 			{{.Title}}
 		</h4>
 		<div class="ui attached segment">
-			<form class="ui form" action="{{.Link}}" method="post">
-				<div id="search-user-box" class="ui search input tw-align-middle">
+			<form class="ui form flex-text-block" action="{{.Link}}" method="post">
+				<div id="search-user-box" class="ui search input">
 					<input class="prompt" name="user" placeholder="{{ctx.Locale.Tr "search.user_kind"}}" autocomplete="off" autofocus required>
 				</div>
 				<button class="ui primary button">{{ctx.Locale.Tr "admin.badges.add_user"}}</button>