Add dashboard defaults (visitor-IP -> business-unit) for kiosk displays

Classic feature gap: a shopfloor/lobby kiosk auto-selects which business unit to
show based on the display PC's IP (classic dashboarddefaults table +
apivisitorlocation.asp). For the main admin dashboard this does nothing - it is
kiosk/visitor-display infra.

- Model: DashboardDefault (dashboarddefaults: ipaddress unique, businessunitid
  FK, description). Migration 7d01_dashboarddefaults (head).
- API (core, /api/dashboarddefaults): CRUD + GET /visitor-location that resolves
  the calling display's business unit from its IP (X-Forwarded-For/remote_addr,
  or explicit ?ipaddress=); unmapped IP returns a null businessunitid, not an
  error. Unauthenticated resolve (kiosks); writes are admin.
- Frontend: ShopfloorDashboard auto-selects its business unit via visitor-location
  on load when none is chosen; Settings > Dashboard Defaults CRUD page +
  dashboardDefaultsApi client.

Tests: create + resolve by IP -> BU; unmapped IP -> null; duplicate IP 409.
191 tests pass, naming green, app boots, endpoint + admin page verified live.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/views/ShopfloorDashboard.vue

@@ -129,7 +129,7 @@
 
 <script setup>
 import { ref, computed, onMounted, onUnmounted } from 'vue'
-import { notificationsApi, businessUnitsApi } from '@/api'
+import { notificationsApi, businessUnitsApi, dashboardDefaultsApi } from '@/api'
 
 const loading = ref(true)
 const businessUnit = ref('')
@@ -176,6 +176,19 @@ onMounted(async () => {
     console.error('Error loading business units:', err)
   }
 
+  // Auto-select this kiosk's business unit from its IP (visitor location),
+  // unless one was already chosen. Falls back to "all" when the IP is unmapped.
+  if (!businessUnit.value) {
+    try {
+      const response = await dashboardDefaultsApi.visitorLocation()
+      if (response.data.data?.businessunitid) {
+        businessUnit.value = response.data.data.businessunitid
+      }
+    } catch (err) {
+      console.error('Error resolving visitor location:', err)
+    }
+  }
+
   await loadData()
 
   // Auto-refresh every 30 seconds