feat(warehouses): persist saved signature image on handover sign

Store the signer's saved-signature URL on booking_handovers (new
signature_image_url column) when a handover is signed — per-truck or
booking-level — so signed handover documents can render the actual
signature, matching the contract-signing flow.

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

apps/edr-freight-api/src/migrations/2800000000001-AddSignatureToHandover.ts

@@ -0,0 +1,22 @@
+import { MigrationInterface, QueryRunner } from 'typeorm';
+
+/**
+ * Persist the signer's saved-signature image on the handover record, so the
+ * signed handover document can render the actual signature (not just the
+ * typed name) — parity with the booking-contract signing flow.
+ */
+export class AddSignatureToHandover2800000000001 implements MigrationInterface {
+  name = 'AddSignatureToHandover2800000000001';
+
+  public async up(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(
+      `ALTER TABLE freight.booking_handovers ADD COLUMN IF NOT EXISTS signature_image_url text;`,
+    );
+  }
+
+  public async down(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(
+      `ALTER TABLE freight.booking_handovers DROP COLUMN IF EXISTS signature_image_url;`,
+    );
+  }
+}