fix: make radio migrations safe for existing schemas

scripts/migration-idempotency.test.ts

@@ -0,0 +1,12 @@
+import { readFileSync } from "node:fs";
+import { resolve } from "node:path";
+import { describe, expect, it } from "vitest";
+
+describe("radio columns migration", () => {
+  it("adds every column idempotently for partially migrated databases", () => {
+    const sql = readFileSync(resolve("prisma/migrations/0009_radio_contests_giveaways_columns.sql"), "utf8");
+    const additions = sql.match(/ADD COLUMN(?! IF NOT EXISTS)/gi) ?? [];
+    expect(additions).toEqual([]);
+    expect(sql).toContain("ADD COLUMN IF NOT EXISTS `title`");
+  });
+});