Add customer Excel import/export and Gama bulk SMS sending.

Business SMS uses optional settings.sms.senderNumber (else advertising shortcode) with SendQuick for one recipient and SendBulk for quantity.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/business-settings/business-settings.types.ts

@@ -195,6 +195,12 @@ export type ModulesSettings = {
   charts: [HomeChartId, HomeChartId];
 };
 
+/** Per-business SMS sender (Gama shortcode). Empty → Meshkee advertising number. */
+export type SmsSettings = {
+  /** Outbound shortcode for customer SMS, e.g. "5000123456". */
+  senderNumber: string | null;
+};
+
 /** Top-level business settings stored in `businesses.settings` JSONB. */
 export type BusinessSettings = {
   branding: BrandingSettings;
@@ -202,6 +208,7 @@ export type BusinessSettings = {
   store: StoreSettings;
   modules: ModulesSettings;
   website: WebsiteSettings;
+  sms: SmsSettings;
 };
 
 export const DEFAULT_ORDER_PROCESS_STEPS: OrderProcessStep[] = [
@@ -316,4 +323,7 @@ export const DEFAULT_BUSINESS_SETTINGS: BusinessSettings = {
   website: {
     specialProductsSource: 'store_item',
   },
+  sms: {
+    senderNumber: null,
+  },
 };