openai service and basic tables with migrations

db/migrations/20260102021640_tenants.sql

@@ -0,0 +1,13 @@
+-- migrate:up
+CREATE EXTENSION IF NOT EXISTS pgcrypto;
+
+CREATE TABLE tenants (
+  id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+  key text NOT NULL UNIQUE,
+  name text NOT NULL,
+  created_at timestamptz NOT NULL DEFAULT now()
+);
+
+-- migrate:down
+DROP TABLE IF EXISTS tenants;
+DROP EXTENSION IF EXISTS pgcrypto;