Allow register to link existing Meshkee accounts after acknowledgement.

Adds optional acknowledgeExistingAccount and documents the CELL_EXISTS_OTHER_SITE → SMS link flow for storefronts.

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

docs/website-api/AI_PROMPT.md

@@ -23,7 +23,7 @@ You are building a **Meshkee business website (storefront)**. You must use the M
 1. Resolve tenant first: `GET /tenants/<WEBSITE_DOMAIN>` → save `businessId` from `id`.
 2. All public content uses `/tenants/<WEBSITE_DOMAIN>/...` (no auth).
 3. Cart, orders, favorites use `/businesses/<businessId>/...` with `Authorization: Bearer <accessToken>`.
-4. Customer register body must include `"domain": "<WEBSITE_DOMAIN>"`.
+4. Customer register body must include `"domain": "<WEBSITE_DOMAIN>"`. If the cell already exists on another Meshkee site and the password differs, API returns `409` with `CELL_EXISTS_OTHER_SITE:...`. Retry register with `"acknowledgeExistingAccount": true` to link that account (password/profile stay unchanged), then complete SMS OTP.
 5. Cell numbers are E.164 (`+98912...`).
 6. Do not call dashboard/CMS routes (`/businesses/.../products` write APIs, media upload, domain-admin, etc.).
 7. **Partner SMS** (`POST /public/sms/send`) is for external partner backends with an issued `X-Api-Key` only — not for normal storefront UI. See https://api.meshkee.com/docs/website/SMS.md

docs/website-api/Meshkee-Website-API.postman_collection.json

@@ -171,7 +171,7 @@
             ],
             "body": {
               "mode": "raw",
-              "raw": "{\n  \"cellNumber\": \"+98XXXXXXXXXX\",\n  \"password\": \"min8chars\",\n  \"firstName\": \"First\",\n  \"lastName\": \"Last\",\n  \"email\": \"optional@example.com\",\n  \"domain\": \"{{domain}}\"\n}"
+              "raw": "{\n  \"cellNumber\": \"+98XXXXXXXXXX\",\n  \"password\": \"min8chars\",\n  \"firstName\": \"First\",\n  \"lastName\": \"Last\",\n  \"email\": \"optional@example.com\",\n  \"domain\": \"{{domain}}\",\n  \"acknowledgeExistingAccount\": false\n}"
             },
             "url": "{{baseUrl}}/auth/register"
           }

docs/website-api/openapi.json

@@ -557,7 +557,11 @@
                   "firstName": { "type": "string" },
                   "lastName": { "type": "string" },
                   "email": { "type": "string" },
-                  "domain": { "type": "string", "description": "Same website apex as {domain}" }
+                  "domain": { "type": "string", "description": "Same website apex as {domain}" },
+                  "acknowledgeExistingAccount": {
+                    "type": "boolean",
+                    "description": "If true, link an existing Meshkee account from another website without matching its password. Existing password and profile stay unchanged."
+                  }
                 }
               }
             }