feat: migrate monthly city trade rates

packages/infra/prisma/game.prisma

@@ -132,7 +132,7 @@ model City {
   security       Int    @map("secu")
   securityMax    Int    @map("secu_max")
   trust          Int    @default(0)
-  trade          Int    @default(100)
+  trade          Int?   @default(100)
   defence        Int    @map("def")
   defenceMax     Int    @map("def_max")
   wall           Int    @map("wall")

packages/infra/prisma/migrations/20260725004000_make_city_trade_nullable/migration.sql

@@ -0,0 +1,2 @@
+ALTER TABLE "city"
+    ALTER COLUMN "trade" DROP NOT NULL;

packages/infra/src/turnEngineDb.ts

@@ -75,7 +75,7 @@ export interface TurnEngineCityRow {
     conflict: JsonValue;
     meta: JsonValue;
     trust: number;
-    trade: number;
+    trade: number | null;
     region: number;
 }
 
@@ -241,7 +241,7 @@ export interface TurnEngineCityUpdateInput {
     conflict?: InputJsonValue;
     meta: InputJsonValue;
     trust?: number;
-    trade?: number;
+    trade?: number | null;
     region?: number;
 }