API endpoints:
/health — quick status/diag — bindings & KV ping/kv-get?asin=B0… — read raw KV entry/bulk-get?asins=B0…,B0… — KV presence list/get-items (POST JSON: { "asins": ["B0…"], "par":8, "ttl":86400, "fresh":0, "order":"aw,dp,m", "t1":6000, "t2":10000, "cacheOnly":0, "debug":0 })/get-items?asin=B0…&cacheOnly=1