Make searchbox first focused element in settings dialog (#5804)

## Summary

Resolves https://github.com/Comfy-Org/ComfyUI_frontend/issues/5164 by
adding `autofocus` prop to common `SearchBox` component then enabled for
the settings dialog search box (changing first focused element from the
close button). Previously, searchbox was the 2nd item in tab order.

## Review Focus

Accessibility implications of automatic focus and potential interference
with screen readers or keyboard navigation patterns. Already discussed
this previously w.r.t. accessibility, but only now implementing.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5804-Make-searchbox-first-focused-element-in-settings-dialog-27a6d73d3650814997facfa2418e1d40)
by [Unito](https://www.unito.io)

src/components/common/SearchBox.vue

@@ -13,6 +13,7 @@
         class="search-box-input w-full"
         :model-value="modelValue"
         :placeholder="placeholder"
+        :autofocus="autofocus"
         @input="handleInput"
       />
       <InputIcon v-if="!modelValue" :class="icon" />
@@ -57,7 +58,8 @@ const {
   icon = 'pi pi-search',
   debounceTime = 300,
   filterIcon,
-  filters = []
+  filters = [],
+  autofocus = false
 } = defineProps<{
   modelValue: string
   placeholder?: string
@@ -65,6 +67,7 @@ const {
   debounceTime?: number
   filterIcon?: string
   filters?: TFilter[]
+  autofocus?: boolean
 }>()
 
 const emit = defineEmits<{

src/platform/settings/components/SettingDialogContent.vue

@@ -6,6 +6,7 @@
         class="settings-search-box w-full mb-2"
         :placeholder="$t('g.searchSettings') + '...'"
         :debounce-time="128"
+        autofocus
         @search="handleSearch"
       />
       <Listbox