chore(emails): add constraint unique email for email_verifications table

packages/server/modules/emails/migrations/20250120145453_add_code_column_to_email_verifications.ts

@@ -5,6 +5,7 @@ const TABLE_NAME = 'email_verifications'
 export async function up(knex: Knex): Promise<void> {
   await knex.schema.alterTable(TABLE_NAME, (table) => {
     table.string('code')
+    table.unique('email')
   })
 }