Move payment_id reference to refactor migration and update schema

The add_reference for event_registrations.payment_id must be in the
branch's refactor migration (not the original payments migration from
main) so it gets applied when CI loads schema.rb then runs pending
migrations.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: maebeale

db/migrate/20260106225822_add_payments_table.rb

@@ -26,6 +26,5 @@ def change
     add_index :payments, [ :payable_type, :payable_id ]
     add_index :payments, [ :payable_type, :payable_id, :status ]
 
-    add_reference :event_registrations, :payment, null: true, foreign_key: true
   end
 end

db/migrate/20260301132706_refactor_payment_associations.rb

@@ -14,5 +14,8 @@ def change
 
     # stripe_payment_intent_id is no longer required
     change_column_null :payments, :stripe_payment_intent_id, true
+
+    # EventRegistration belongs_to :payment (singular, direct FK)
+    add_reference :event_registrations, :payment, null: true, foreign_key: true
   end
 end

db/schema.rb

@@ -684,7 +684,7 @@
     t.string "failure_message"
     t.integer "organization_id"
     t.bigint "payer_id", null: false
-    t.string "payment_type", default: "stripe", null: false
+    t.string "payment_type", default: "other", null: false
     t.string "status", null: false
     t.string "stripe_charge_id"
     t.json "stripe_metadata"