First-run setup wizard (/setup)

- setup_complete site setting; a fresh admin is steered to /setup until it is
  finished (skippable for the session).
- SetupWizard.vue: Site (facility/base-url/access-domain), Features (plugin
  enable/disable), Floor Map dimensions, Starter Data (seed common vendors),
  Finish. Reuses the settings + plugins APIs.
- setup blueprint: POST /setup/seed-starter (idempotent common vendors) and
  POST /setup/complete. setupState composable drives the router redirect.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/api/index.js

@@ -754,6 +754,15 @@ export const pluginsApi = {
   }
 }
 
+export const setupApi = {
+  seedStarter() {
+    return api.post('/setup/seed-starter')
+  },
+  complete() {
+    return api.post('/setup/complete')
+  }
+}
+
 export const settingsApi = {
   list(params = {}) {
     return api.get('/settings', { params })