feat(base): add migration marker for formula property type

apps/server/src/database/migrations/20260419T120000-base-formula-property-type.ts

@@ -0,0 +1,15 @@
+import { type Kysely, sql } from "kysely";
+
+/*
+ * The `base_properties.type` column is varchar with no CHECK constraint
+ * in the current schema, so runtime validation of 'formula' happens entirely
+ * in the Zod layer (base.schemas.ts). This migration is intentionally empty —
+ * it exists to mark the formula property type release in the migration log.
+ */
+export async function up(_db: Kysely<any>): Promise<void> {
+  // no-op — formula type allowed at Zod layer
+}
+
+export async function down(_db: Kysely<any>): Promise<void> {
+  // no-op
+}