feat(manifest): add externalNumber reference to quote/order/delivery

- Add `external_number NVARCHAR(100)` column to the `manifest` table.
- Thread `externalNumber` through manifestDoc and delivery SQL (list,
  header, create, update).
- Include `externalNumber` in shapeSummary and quote/order/delivery
  create/update/list/getById handlers (optional, clearable on update).
- Update README type definitions and regenerate API/schema docs.

src/store/delivery/getById.js

@@ -9,12 +9,12 @@ export default function getById(pool) {
    *
    * @param {number} googleAuthId - The id of the Google auth user.
    * @param {number} id - The id of the delivery.
-   * @returns {Promise<{id: number, number: string, type: string, entityId: number, date: string, lines: Array<object>}>} The delivery.
+   * @returns {Promise<{id: number, number: string, type: string, entityId: number, externalNumber: string|null, date: string, lines: Array<object>}>} The delivery.
    * @throws {Error} If the delivery is not found.
    *
    * @example
    * const delivery = await store.delivery.getById(42, 5);
-   * // => { id, number, type, entityId, date, lines: [...] }
+   * // => { id, number, type, entityId, externalNumber, date, lines: [...] }
    */
   return async (googleAuthId, id) => {
     if (!Number.isFinite(id)) {