feat(train-scheduling): mid-route consist changes, audit history, safer workspace

- planned couples: loose wagons join the train at a route stop, added
  from the schedule yards tab; capacity credits them per corridor edge
  and coupling validates locomotive weight/length caps per leg
- real-cut toggle: a cut wagon permanently leaves the train build at
  its cut yard (soft cut still sits out one trip only)
- fix heaviest-leg display counting a shared slot's full cargo on
  every spanned edge (phantom pull-weight overload on S-2026-00045)
- confirmation dialogs for workspace add/load/unload/remove actions
- train-builder History and Detached-wagons tabs, backed by paginated
  endpoints; builder detaches now always write adjustment-log rows

Migrations 3660 (planned_wagon_couples, planned_wagon_real_cuts) and
3670 (adjustment log train_schedule_id nullable) — both applied to the
dev DB by hand; watch mode does not run migrations.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

apps/edr-freight-api/src/modules/train-scheduling/edge-load.util.ts

@@ -0,0 +1,50 @@
+/**
+ * Per-corridor-edge physical load of a train: tare + length of the wagons
+ * spanning each edge, plus the cargo weight riding it. Used to validate that
+ * a planned mid-route COUPLE keeps every leg within the locomotives' pull
+ * weight and train length limits — a wagon cut at Mojo frees its tare/length
+ * on the edges past Mojo, a wagon coupled there adds its own only from there.
+ */
+
+export interface EdgeLoad {
+  weightTons: number;
+  lengthMeters: number;
+}
+
+export interface EdgeWagonSpan {
+  /** Half-open edge span [fromEdge, toEdge) the wagon physically rides. */
+  fromEdge: number;
+  toEdge: number;
+  tareTons: number;
+  lengthMeters: number;
+}
+
+export interface EdgeCargoLeg {
+  fromEdge: number;
+  toEdge: number;
+  weightTons: number;
+}
+
+export function computeEdgeLoads(
+  edgeCount: number,
+  wagonSpans: readonly EdgeWagonSpan[],
+  cargoLegs: readonly EdgeCargoLeg[],
+): EdgeLoad[] {
+  const loads: EdgeLoad[] = Array.from({ length: Math.max(1, edgeCount) }, () => ({
+    weightTons: 0,
+    lengthMeters: 0,
+  }));
+  const clamp = (edge: number) => Math.min(Math.max(edge, 0), loads.length);
+  for (const span of wagonSpans) {
+    for (let e = clamp(span.fromEdge); e < clamp(span.toEdge); e += 1) {
+      loads[e].weightTons += span.tareTons;
+      loads[e].lengthMeters += span.lengthMeters;
+    }
+  }
+  for (const cargo of cargoLegs) {
+    for (let e = clamp(cargo.fromEdge); e < clamp(cargo.toEdge); e += 1) {
+      loads[e].weightTons += cargo.weightTons;
+    }
+  }
+  return loads;
+}