feat: review comments

backend/src/db/migrations/20250908193226_sql-cache_int.ts

@@ -8,6 +8,7 @@ export async function up(knex: Knex): Promise<void> {
       t.text("key").primary();
       t.bigint("integerValue");
       t.datetime("expiresAt");
+      t.timestamps(true, true, true);
     });
   }
 }

backend/src/db/schemas/key-value-store.ts

@@ -10,7 +10,9 @@ import { TImmutableDBKeys } from "./models";
 export const KeyValueStoreSchema = z.object({
   key: z.string(),
   integerValue: z.coerce.number().nullable().optional(),
-  expiresAt: z.date().nullable().optional()
+  expiresAt: z.date().nullable().optional(),
+  createdAt: z.date(),
+  updatedAt: z.date()
 });
 
 export type TKeyValueStore = z.infer<typeof KeyValueStoreSchema>;