orders: cast cadence order_count to int — BigInt broke every recurring merchant

order_merchant_cadence.order_count is a count(*), so BIGINT, and JSON.stringify
throws on it: 'Do not know how to serialize a BigInt', a 500 carrying no SQL.
It fires only where a cadence EXISTS, so the failure hid behind the
merchant_entity_id fault and reappeared the moment that was fixed — St. Ali
(40 orders, 14-day cadence) still 500'd while Amazon opened fine.

src/lib/order-feed.ts

@@ -399,7 +399,13 @@ export async function getOrderDetail(entityKey: string): Promise<OrderDetail | n
             ctx.content_class,
             COALESCE(me2.canonical_name, ctx.counterparty, o.platform) AS display_name,
             rec.cadence_days,
-            rec.order_count
+            -- ::int is mandatory. order_merchant_cadence.order_count is a
+            -- count(*), so BIGINT, and JSON.stringify throws outright on a
+            -- BigInt — "Do not know how to serialize a BigInt", a 500 with no
+            -- SQL in it. It only fires on merchants that HAVE a cadence, so
+            -- most orders open fine and the recurring ones die; testing one
+            -- arbitrary order will not find it.
+            rec.order_count::int AS order_count
        FROM entities e
        JOIN entity_orders o ON o.entity_id = e.id
        LEFT JOIN entities m ON m.id = o.merchant_entity_id