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/vite.config.js

@@ -17,6 +17,8 @@ const MIGRATED_ROUTES = {
   '/panel/': '/index.html',
   '/panel/settings': '/settings.html',
   '/panel/settings/': '/settings.html',
+  '/panel/inbounds': '/inbounds.html',
+  '/panel/inbounds/': '/inbounds.html',
 };
 
 // Build a proxy config that suppresses ECONNREFUSED noise when the Go
@@ -69,6 +71,7 @@ export default defineConfig({
         index: path.resolve(__dirname, 'index.html'),
         login: path.resolve(__dirname, 'login.html'),
         settings: path.resolve(__dirname, 'settings.html'),
+        inbounds: path.resolve(__dirname, 'inbounds.html'),
       },
     },
   },