refactor(shortcut): Use declarative data attributes for keyboard shortcuts

Instead of having JavaScript code guess which elements exist on a page,
elements now declare their keyboard shortcuts via data-global-keyboard-shortcut
attribute. This makes it easier to add new shortcuts and follows Gitea's
existing patterns for data-global-init and data-global-click.

web_src/js/components/RepoFileSearch.vue

@@ -150,6 +150,7 @@ watch([searchQuery, filteredFiles], async () => {
       <input
         ref="searchInput" :placeholder="placeholder" autocomplete="off"
         role="combobox" aria-autocomplete="list" :aria-expanded="searchQuery ? 'true' : 'false'"
+        data-global-keyboard-shortcut="t"
         @input="handleSearchInput" @keydown="handleKeyDown"
         @focus="isInputFocused = true" @blur="isInputFocused = false"
       >