Add customer SMS/Excel tools, selection bar, and sticky import toasts.

Bulk and single SMS from Users, row selection with overflow summary, persistent large import toasts, and business SMS sender in Super Admin.

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

docs/PROJECT_CONTEXT.md

@@ -3,7 +3,7 @@
 > **For AI agents:** Read this file at the start of a new chat before making changes.  
 > Update this document when a major feature is completed or architecture changes.
 
-Last updated: September 3, 2026
+Last updated: September 8, 2026
 
 ---
 
@@ -313,6 +313,11 @@ Products accept optional `brandId` on create/update.
 ### Customers
 - `GET/POST/PATCH/DELETE /businesses/:businessId/customers`
 - `GET /businesses/:businessId/customers/search` — autocomplete for order cart
+- `GET /businesses/:businessId/customers/export` — Excel (.xlsx) of business customers (`phone`, `first_name`, `last_name`)
+- `POST /businesses/:businessId/customers/import` — Excel import for SMS lists; only `phone` required; new users get a random password hash (OTP login still works); existing users are linked; already-linked / staff rows skipped
+- `POST /businesses/:businessId/customers/:userId/sms` — single SMS via Gama **SendQuick**; uses `settings.sms.senderNumber` or advertising shortcode `5000990009`
+- `POST /businesses/:businessId/customers/sms` — bulk SMS via Gama **SendBulk** (`destinations[]`); body `{ message, userIds? }` — empty/omitted `userIds` → all enabled customers; selected ids → those recipients
+- Super Admin business edit: optional **SMS sender number** stored in `businesses.settings.sms.senderNumber`
 
 ### Orders
 - `GET/POST/PATCH/DELETE /businesses/:businessId/orders`