fix(systemtags): Include leading slash in unified search tag link

Tag results from unified search opened the tags view with a directory
path missing its leading slash, which the view rejected with "Invalid
tag ID". Tag links now match the path convention used elsewhere so the
tag opens correctly and lists the files associated with it.

Author: nfebe

apps/systemtags/lib/Search/TagSearchProvider.php

@@ -102,7 +102,7 @@ public function search(IUser $user, ISearchQuery $query): SearchResult {
 			$thumbnailUrl = '';
 			$link = $this->urlGenerator->linkToRoute('files.view.indexView', [
 				'view' => 'tags',
-			]) . '?dir=' . $tag->getId();
+			]) . '?dir=/' . $tag->getId();
 			$searchResultEntry = new SearchResultEntry(
 				$thumbnailUrl,
 				$this->l10n->t('All tagged %s …', [$tag->getName()]),