feat: tiered billing (cloud) (#1294)

* feat: tiered billing (cloud)

* custom tier

apps/server/src/database/migrations/20250623T215045-more-billing-columns.ts

@@ -0,0 +1,23 @@
+import { type Kysely } from 'kysely';
+
+export async function up(db: Kysely<any>): Promise<void> {
+  await db.schema
+    .alterTable('billing')
+    .addColumn('billing_scheme', 'varchar', (col) => col)
+    .addColumn('tiered_up_to', 'varchar', (col) => col)
+    .addColumn('tiered_flat_amount', 'int8', (col) => col)
+    .addColumn('tiered_unit_amount', 'int8', (col) => col)
+    .addColumn('plan_name', 'varchar', (col) => col)
+    .execute();
+}
+
+export async function down(db: Kysely<any>): Promise<void> {
+  await db.schema
+    .alterTable('billing')
+    .dropColumn('billing_scheme')
+    .dropColumn('tiered_up_to')
+    .dropColumn('tiered_flat_amount')
+    .dropColumn('tiered_unit_amount')
+    .dropColumn('plan_name')
+    .execute();
+}