feat(db): Customer.cityNameRaw for the city typed at legacy sign-up

Additive and nullable. Owner ruling 2026-10-07: keep the typed text
verbatim, and set cityId as well only on an exact match.

Legacy customers.new_city is free text: all 172 live values are names,
none are ids. The legacy city table has only 15 rows and 43 of the names
match no city, so dropping the text would lose where those customers are.
Legacy sign-up also forced city_id = 5 (Tehran) on everyone
(Major/CustomerController.php:21). 91 of the 92 customers with both
values carry that forced Tehran, so the typed name is the truth.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/api/prisma/schema.prisma

@@ -390,6 +390,16 @@ model Customer {
   cityId       String?
   city         City?   @relation(fields: [cityId], references: [id])
 
+  /// Legacy customers.new_city — the city name exactly as the customer typed it
+  /// at app sign-up (Major/CustomerController.php:36). Kept verbatim because
+  /// the legacy city table has only 15 rows, so the typed name is often the only
+  /// record of where the customer is (172 customers; 43 match no known city).
+  /// cityId is set alongside it only on an exact, ي/ك-normalised name match.
+  /// Legacy sign-up also forced city_id = 5 (Tehran) on everyone
+  /// (Major/CustomerController.php:21), so for those rows the typed name, not
+  /// cityId, is the truth. Owner ruling 2026-10-07: keep both.
+  cityNameRaw String?
+
   /// Legacy Customer.type — distinguishes بنکدار from مغازه دار, which the
   /// BankerList / ShopkeeperList screens filter on.
   kind CustomerKind @default(APP_SHOPKEEPER)