feat(warehouses): track physical container stack and slot positions

Extends the warehouse hierarchy below zone with ground stacks and vertical
slots, so a container's exact position is recorded rather than only its zone.

- freight.warehouse_zone_stacks / warehouse_zone_slots, plus nullable
  stack_id / slot_id on warehouse_inventory (existing rows stay valid)
- slot occupancy is derived from inventory status, guarded by a partial
  unique index, so no exit path has to remember to free a slot
- placement service: hierarchy validation, bottom-up stacking rules,
  accessibility/blocking-container reads, capacity vs slot summaries
- stack CRUD with auto-generated slots; reuses warehouse-zone permissions
- slot support folded into the existing move()/store() paths
- fix: validateLocation now rejects a mismatched warehouse/yard/zone triple
- seed:warehouse-layout builds the layout from a JSON config

apps/edr-freight-web/backoffice/src/components/warehouses/ZoneContentsModal.tsx

@@ -4,12 +4,19 @@ import { DataTable, type ColumnDef } from '@edr/ui-common';
 
 import { formatDateTime, humanize } from '@/lib/format';
 import { api } from '@/services/api';
-import type { WarehouseZone, ZoneContentItem } from '@/types/warehouse';
+import type { ZoneContentItem } from '@/types/warehouse';
+
+/** Enough to name the zone and fetch it — satisfied by WarehouseZone and ZoneOccupancy alike. */
+export interface ZoneRef {
+  id: string;
+  name: string;
+  code: string;
+}
 
 interface ZoneContentsModalProps {
   opened: boolean;
   onClose: () => void;
-  zone: WarehouseZone | null;
+  zone: ZoneRef | null;
 }
 
 const columns: ColumnDef<ZoneContentItem>[] = [

apps/edr-freight-web/backoffice/src/components/warehouses/ZoneOccupancyHeatmap.tsx

@@ -25,13 +25,15 @@ function capacityLabel(z: ZoneOccupancy): string {
 interface ZoneOccupancyHeatmapProps {
   /** Scope to one yard; omit for all zones. */
   yardId?: string;
+  /** Pass to make each tile open that zone; omitted leaves the tiles inert. */
+  onZoneClick?: (zone: ZoneOccupancy) => void;
 }
 
 /**
  * Occupancy heatmap: one tile per zone, coloured by how full it is. Occupancy is
  * container-count based (unit-consistent); weight is shown as context only.
  */
-export function ZoneOccupancyHeatmap({ yardId }: ZoneOccupancyHeatmapProps) {
+export function ZoneOccupancyHeatmap({ yardId, onZoneClick }: ZoneOccupancyHeatmapProps) {
   const { data: zones = [], isLoading } = useZoneOccupancy(yardId);
 
   if (isLoading) {
@@ -67,7 +69,15 @@ export function ZoneOccupancyHeatmap({ yardId }: ZoneOccupancyHeatmapProps) {
           const t = tone(z.occupancyPct);
           const pct = z.occupancyPct ?? 0;
           return (
-            <Card key={z.id} withBorder radius="md" padding="sm">
+            <Card
+              key={z.id}
+              withBorder
+              radius="md"
+              padding="sm"
+              onClick={onZoneClick ? () => onZoneClick(z) : undefined}
+              style={onZoneClick ? { cursor: 'pointer' } : undefined}
+              title={onZoneClick ? `View what is stored in ${z.name}` : undefined}
+            >
               <Stack gap={6}>
                 <Group justify="space-between" wrap="nowrap" gap="xs">
                   <Text fw={600} size="sm" truncate title={z.name}>

apps/edr-freight-web/backoffice/src/components/warehouses/index.ts

@@ -9,7 +9,7 @@ export { WarehouseInquiryTable } from './WarehouseInquiryTable';
 export { CreateWarehouseModal } from './CreateWarehouseModal';
 export { CreateYardModal } from './CreateYardModal';
 export { CreateZoneModal } from './CreateZoneModal';
-export { ZoneContentsModal } from './ZoneContentsModal';
+export { ZoneContentsModal, type ZoneRef } from './ZoneContentsModal';
 export { ReceiveInventoryModal, WarehouseFlowWorkbench } from './ReceiveInventoryModal';
 export { WarehouseInfoCard } from './WarehouseInfoCard';
 export { MoveInventoryModal } from './MoveInventoryModal';

apps/edr-freight-web/backoffice/src/pages/warehouses/WarehouseDetailPage.tsx

@@ -24,6 +24,7 @@ import {
   WarehouseStatusBadge,
   WarehouseTypeBadge,
   ZoneContentsModal,
+  type ZoneRef,
   ZoneOccupancyHeatmap,
   formatCapacity,
   humanizeEnum,
@@ -61,7 +62,7 @@ export default function WarehouseDetailPage() {
   const [zoneModalOpen, setZoneModalOpen] = useState(false);
   const [editingZone, setEditingZone] = useState<WarehouseZone | null>(null);
   const [selectedYardId, setSelectedYardId] = useState<string | null>(null);
-  const [contentsZone, setContentsZone] = useState<WarehouseZone | null>(null);
+  const [contentsZone, setContentsZone] = useState<ZoneRef | null>(null);
 
   const zonesQuery = useQuery(
     api.warehouses.listZones.queryOptions({
@@ -373,7 +374,10 @@ export default function WarehouseDetailPage() {
                 </Button>
               </Group>
 
-              <ZoneOccupancyHeatmap yardId={selectedYardId ?? undefined} />
+              <ZoneOccupancyHeatmap
+                yardId={selectedYardId ?? undefined}
+                onZoneClick={(zone) => setContentsZone(zone)}
+              />
 
               {!selectedYardId ? (
                 <Text c="dimmed" ta="center" py="lg">