feat: implement business pricing service and money utilities

- Added `businessPricing.service.js` to handle business customer pricing logic.
- Introduced `money.js` for money parsing, formatting, and calculations.
- Created `pricing.service.js` to manage variant quoting and promotion application.
- Updated validation schemas in `catalogue.schemas.js` and `inventoryMerchandising.schemas.js` for new pricing and inventory features.
- Implemented cron job for inventory reservation expiry in `inventoryReservationExpiry.cron.js`.
- Created database migrations for catalogue and inventory structures.
- Added unit tests for catalogue localization, validation, and inventory merchandising functionalities.

Documentation/API_INVENTORY_MERCHANDISING.md

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+# Inventory and Merchandising API
+
+All routes use the `/api/v1` prefix. Admin routes require authentication and the named Phase 5 permission.
+
+## Inventory and warehouses
+
+- `GET /admin/inventory` (`inventory.read`)
+- `GET /admin/inventory/:variantId` (`inventory.read`)
+- `GET /admin/inventory/ledger` (`inventory.read`)
+- `GET /admin/inventory/low-stock` (`inventory.read`)
+- `POST /admin/inventory/adjustments` (`inventory.adjust`); send `Idempotency-Key`
+- `POST /admin/inventory/transfers` (`inventory.transfer`); send `Idempotency-Key`
+- `GET /admin/warehouses` (`inventory.read`)
+- `POST /admin/warehouses`, `PATCH /admin/warehouses/:id` (`inventory.warehouses.manage`)
+- `GET /availability/:variantId` returns only `IN_STOCK`, `LOW_STOCK`, or `OUT_OF_STOCK` and `availableForSale`; it never exposes warehouse quantities.
+
+Inventory mutations are internal service operations: `reserveStock`, `releaseReservation`, and `consumeReservation`. Reservations default to `INVENTORY_RESERVATION_TTL_MINUTES=15`. The minute reconciliation job expires bounded batches of 100; the database remains authoritative.
+
+## Business pricing
+
+- `GET /admin/business-pricing` (`pricing.business.read`)
+- `POST /admin/business-pricing` (`pricing.business.manage`)
+
+Rules support exactly one tier or customer audience, effective dates, MOQ, and non-overlapping volume ranges. Precedence is customer override, business tier, then retail. Money is stored as DECIMAL and calculated using integer-scaled helpers.
+
+## Promotions and coupons
+
+- `GET|POST /admin/promotions` (`promotions.read` / `promotions.manage`)
+- `GET|POST /admin/coupons` (`promotions.read` / `promotions.manage`)
+
+The quote boundary resolves retail/business base price, then the highest-priority eligible automatic promotion, then a coupon only when stacking permits. Discounts floor at zero. Coupon codes are canonical uppercase. Usage redemption is intentionally deferred until orders exist.
+
+## Banners
+
+- `GET /banners?placement=&locale=` returns active, scheduled, audience-eligible localized banners.
+- `GET|POST /admin/banners` requires `merchandising.banners.manage`.
+
+Banner media reuses Upload records and only returns safe upload identifiers, never bucket/object keys.
+
+## Not implemented
+
+Cart, checkout, orders, coupon redemption, shipping, tax, payment, and delivery remain outside Phase 5.