Add Mellat e-payment, videos/instructions CMS, and legacy domain lookup.

Store gateway credentials per business, initiate/verify Mellat at checkout, and resolve old CMS ids from domains in the migrate modal.

Co-authored-by: Cursor <cursoragent@cursor.com>

database/migrations/060_videos_old_id.sql

@@ -0,0 +1,7 @@
+ALTER TABLE videos ADD COLUMN IF NOT EXISTS old_id BIGINT;
+
+CREATE UNIQUE INDEX IF NOT EXISTS videos_business_old_id_unique
+  ON videos (business_id, old_id)
+  WHERE old_id IS NOT NULL;
+
+CREATE INDEX IF NOT EXISTS idx_videos_old_id ON videos (old_id);