feat(warehouses): backoffice UI for container stack positions

Surfaces the physical stack/slot model in the staff app.

- ZoneLayoutModal: stacks drawn level by level with occupancy colours,
  configured-vs-built-vs-occupied counts, and stack create/delete plus
  block/reserve/free on empty levels
- SlotPicker in the store and move modals, offering only the next
  fillable level of each stack so the form cannot suggest a position
  the API will refuse
- move modal warns when a container is buried, lists the blockers, and
  disables the action instead of firing a 409
- fix: move() now asserts accessibility server-side, matching release —
  both are exits from a stack

apps/edr-freight-web/backoffice/src/constants/URLS.ts

@@ -652,6 +652,16 @@ export const URL_CONSTANTS = {
   WAREHOUSE_ZONES: {
     BASE: "/warehouse-zones",
     BY_ID: (id: string) => `/warehouse-zones/${id}`,
+    LAYOUT: (id: string) => `/warehouse-zones/${id}/layout`,
+    SLOT_SUMMARY: (id: string) => `/warehouse-zones/${id}/slot-summary`,
+  },
+
+  WAREHOUSE_ZONE_STACKS: {
+    BASE: "/warehouse-zone-stacks",
+    BY_ZONE: (zoneId: string) => `/warehouse-zone-stacks?zoneId=${zoneId}`,
+    BY_ID: (id: string) => `/warehouse-zone-stacks/${id}`,
+    OCCUPANCY: (id: string) => `/warehouse-zone-stacks/${id}/occupancy`,
+    SLOT: (slotId: string) => `/warehouse-zone-stacks/slots/${slotId}`,
   },
 
   WAREHOUSE_INVENTORY: {
@@ -666,6 +676,10 @@ export const URL_CONSTANTS = {
     LOAD: (id: string) => `/warehouse-inventory/${id}/load`,
     DISPATCH: (id: string) => `/warehouse-inventory/${id}/dispatch`,
     MOVE: (id: string) => `/warehouse-inventory/${id}/move`,
+    FIND_SLOT: "/warehouse-inventory/placement/find-slot",
+    ASSIGN_SLOT: (id: string) => `/warehouse-inventory/${id}/assign-slot`,
+    RELEASE_SLOT: (id: string) => `/warehouse-inventory/${id}/release-slot`,
+    ACCESSIBILITY: (id: string) => `/warehouse-inventory/${id}/accessibility`,
     RESERVE: "/warehouse-inventory/reserve",
     ARRIVAL_QUEUE: "/warehouse-inventory/arrival-queue",
     OPS_STATS: "/warehouse-inventory/ops-stats",