feat(BE-58,59,60,61): implement stock transfer API, validation, audit log, and schema update

- Build stock transfer API with nested details, deliveries, and items
- Extend DB schema for stock transfers
- Implement validation for transfer request and stock
- Prepare/implement transfer audit log structure
- Preload all relations for complete response
- Update DTOs for nested response
- Remove redundant root fields, use relation objects

internal/database/migrations/20250925040409_create_master_tables.up.sql

@@ -316,7 +316,7 @@ CREATE TABLE stock_logs (
     before_quantity NUMERIC(15, 3) NOT NULL,
     after_quantity NUMERIC(15, 3) NOT NULL,
     log_type VARCHAR(50) NOT NULL,
-    log_id BIGINT ,
+    log_id BIGINT,
     note TEXT,
     product_warehouse_id BIGINT NOT NULL REFERENCES product_warehouses (id) ON DELETE CASCADE ON UPDATE CASCADE,
     created_by BIGINT NOT NULL REFERENCES users (id) ON DELETE SET NULL ON UPDATE CASCADE,