feat(frontend): Phase 5f-i — inbounds page shell + list fetch

Adds the inbounds entry as a fourth Vite multi-page input and wires
/panel/inbounds through the dev proxy bypass. Lays down the page
chrome (sidebar, summary statistics card, refresh button) and the
fetch lifecycle composable so 5f-ii onward can drop in the table
columns and the modals without re-implementing it.

- inbounds.html + src/inbounds.js: fourth Vite entry; mounts InboundsPage.
- InboundsPage.vue: sidebar + summary card (totals over up/down,
  all-time, inbound count, client tags) + a basic table with enable/
  remark/port/protocol/traffic/expiry columns. Row actions, popovers,
  search/filter, auto-refresh, and the WebSocket delta path are all
  deferred to subsequent 5f subphases.
- useInbounds.js composable: GET /panel/api/inbounds/list +
  POST /panel/api/inbounds/onlines + POST /panel/api/inbounds/lastOnline +
  POST /panel/setting/defaultSettings, then computes the
  per-inbound clientCount roll-ups (active/deactive/depleted/expiring/
  online/comments) the table popovers consume.
- models/dbinbound.js + models/inbound.js: switched the legacy-utils
  import to the @/utils alias for consistency with the rest of the
  app. Semantics unchanged.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/models/dbinbound.js

@@ -1,4 +1,4 @@
-import { ObjectUtil, NumberFormatter, SizeFormatter } from '../utils/legacy.js';
+import { ObjectUtil, NumberFormatter, SizeFormatter } from '@/utils';
 import { Inbound, Protocols } from './inbound.js';
 
 export class DBInbound {

frontend/src/models/inbound.js

@@ -1,4 +1,4 @@
-import { ObjectUtil, RandomUtil, Base64 } from '../utils/legacy.js';
+import { ObjectUtil, RandomUtil, Base64 } from '@/utils';
 
 export const Protocols = {
     VMESS: 'vmess',