Support subpath IIS deployment as a second install method

The app can run as an IIS Application under an existing site
(e.g. https://host/ops/) instead of its own site + port:

- frontend: vite base via VITE_BASE_PATH; router history, axios
  baseURL, and root-absolute asset/route paths resolve through
  utils/basePath.js withBase()
- backend: MOUNT_PATH (env or .env) wraps the app in a WSGI
  middleware that shifts the prefix into SCRIPT_NAME, so one knob
  serves API + SPA under the mount
- docs: INSTALL-WINDOWS-IIS.md section 7b runbook + troubleshooting
  rows; DEPLOY-WINDOWS-IIS.md pointer; commented examples in
  deploy/windows/web.config and .env.example

Root deployment unchanged (MOUNT_PATH unset, base '/'). Also folds
two stray root-absolute callers into the shared plumbing
(MachineForm relationship-types fetch, reports CSV window.open).

frontend/src/views/ShopfloorDashboard.vue

@@ -186,10 +186,11 @@
 import { ref, computed, onMounted, onUnmounted } from 'vue'
 import { notificationsApi, businessUnitsApi, dashboardDefaultsApi } from '@/api'
 import { getFacilityName, getSiteLogo, getServicenowUrls } from '@/utils/siteSettings'
+import { withBase } from '@/utils/basePath'
 
 const loading = ref(true)
 const facilityName = ref('ShopDB')
-const siteLogo = ref('/ge-aerospace-logo.svg')
+const siteLogo = ref(withBase('/ge-aerospace-logo.svg'))
 // ServiceNow ticket-link config; loaded on mount. Empty/disabled = plain text.
 const servicenowConfig = ref({ enabled: true, incidentUrl: '', changeUrl: '' })
 const businessUnit = ref('')