add yard distances management to rule engine

- Introduced new yard distances resource with CRUD operations.
- Created migration for yard distances table with necessary constraints.
- Implemented service and repository for yard distances handling.
- Added controller for API endpoints to manage yard distances.
- Updated rule engine configuration to include yard distances.
- Enhanced rule engine resource page to support yard distance selection.
- Updated contracts and train builder pages to handle new yard distance logic.
- Added error handling utility for better error message extraction.

apps/edr-freight-web/backoffice/src/components/trainBuilder/BuildTrainModal.tsx

@@ -46,10 +46,18 @@ export default function BuildTrainModal({ opened, onClose, onBuilt }: BuildTrain
   // Admin-managed run list (dropdown settings); numbers already on a train
   // come back disabled so they cannot be picked twice.
   const importNumbers = useImportTrainNumberOptions();
-  // Only serviceable locomotives standing in the selected yard can be coupled.
+  // Only serviceable locomotives standing in the selected yard, and not already
+  // coupled to another built train, can be picked. A new train owns none yet, so
+  // no train to keep-exclude.
   const locomotivesQuery = useQuery(
     api.locomotives.listFiltered.queryOptions({
-      input: { filters: { status: "AVAILABLE", currentYardId: yardId } },
+      input: {
+        filters: {
+          status: "AVAILABLE",
+          currentYardId: yardId,
+          excludeCoupled: true,
+        },
+      },
       enabled: Boolean(yardId),
     }),
   );

apps/edr-freight-web/backoffice/src/components/trainBuilder/ChangeLocomotivesModal.tsx

@@ -26,9 +26,19 @@ export default function ChangeLocomotivesModal({
   const [locomotiveIds, setLocomotiveIds] = useState<string[]>([]);
 
   const yardId = composition?.currentYard?.id ?? "";
+  // A locomotive already coupled to ANOTHER built train is not a valid pick —
+  // the API rejects it on save. Exclude those here (keeping this train's own
+  // ones, which are re-listed below as "(coupled)").
   const availableQuery = useQuery(
     api.locomotives.listFiltered.queryOptions({
-      input: { filters: { status: "AVAILABLE", currentYardId: yardId } },
+      input: {
+        filters: {
+          status: "AVAILABLE",
+          currentYardId: yardId,
+          excludeCoupled: true,
+          excludeTrainId: composition?.id,
+        },
+      },
       enabled: opened && Boolean(yardId),
     }),
   );

apps/edr-freight-web/backoffice/src/components/trainBuilder/trainStatus.ts

@@ -28,6 +28,34 @@ export const trainStatusLabel = (status: BuiltTrainStatus | string): string =>
     .replace(/_/g, " ")
     .replace(/^\w/, (c) => c.toUpperCase());
 
+/** Statuses that block a deactivated train from reactivating (mirrors the API gate). */
+export const UNFIT_LOCOMOTIVE_STATUSES = new Set(["MAINTENANCE", "OUT_OF_SERVICE", "UNAVAILABLE"]);
+
+/** Badge color per locomotive status (Mantine palette keys). */
+export const locomotiveStatusColor = (status: string): string => {
+  switch (status) {
+    case "AVAILABLE":
+    case "IMPORT_READY":
+    case "EXPORT_READY":
+      return "edr-green";
+    case "ASSIGNED":
+      return "blue";
+    case "MAINTENANCE":
+      return "yellow";
+    case "OUT_OF_SERVICE":
+    case "UNAVAILABLE":
+      return "red";
+    default:
+      return "gray";
+  }
+};
+
+export const locomotiveStatusLabel = (status: string): string =>
+  String(status)
+    .toLowerCase()
+    .replace(/_/g, " ")
+    .replace(/^\w/, (c) => c.toUpperCase());
+
 /** Badge color per trade direction (Mantine palette keys). */
 export const directionColor = (direction?: string | null): string =>
   direction === "IMPORT" ? "blue" : direction === "EXPORT" ? "orange" : "gray";