fix: rename migration 0039_app_settings to 0041 to avoid conflict with 0039_cash-rounding

packages/backend/src/db/migrations/0041_app_settings.sql

@@ -0,0 +1,8 @@
+CREATE TABLE IF NOT EXISTS "app_settings" (
+  "key" varchar(100) PRIMARY KEY,
+  "value" text,
+  "is_encrypted" boolean NOT NULL DEFAULT false,
+  "iv" text,
+  "created_at" timestamptz NOT NULL DEFAULT now(),
+  "updated_at" timestamptz NOT NULL DEFAULT now()
+);