Add Super Admin AI prompt templates and business assignment UI.

Templates library plus per-business prompt list with edit, copy public link, and remove.

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

docs/PROJECT_CONTEXT.md

@@ -143,6 +143,7 @@ Add to `/etc/hosts` (one line per tenant):
 | `/businesses/:businessId/invoices/new` | Issue invoice (full page) |
 | `/users` | Users (business filter: Customer vs Manager → Admin/Editor/Viewer; Admin assignable by super-admin only; owners locked) |
 | `/websites` | Websites / domains (Deploy when `deploy_slug` set). Edit domain can optionally update Arvan DNS. |
+| `/templates` | Global AI prompt templates. Assign from Businesses ⋯ → **AI prompts** (add from library; public pack link). |
 | `/settings` | Platform settings (invoice templates + item templates) |
 | `/settings/invoice-templates/new` | Create invoice template |
 | `/settings/invoice-templates/:templateId` | Edit invoice template |