chore: park worker, recommend cron-job.org as primary scheduler

Comment out [triggers].crons in wrangler.toml — migrated this routine to
cron-job.org (free, verified) to keep the CF cron-trigger free-tier quota
available for other workers. Worker code, secrets, and observability
config stay intact so re-enabling is one toml uncomment + redeploy.

README restructured: lead with cron-job.org setup (signup → headers → JSON
body), demote CF Worker setup to a secondary path under "Using Cloudflare
Workers" for users who specifically want CF infra.

cloudflare-worker/wrangler.toml

@@ -11,13 +11,15 @@ TZ = "Asia/Ho_Chi_Minh"
 
 # Cron triggers fire from this list. CF Workers requires literal cron
 # expressions here — they cannot be loaded from env vars or secrets.
-# Schedule (Asia/Ho_Chi_Minh, UTC+7): hourly at :00 from 05:00 to 23:00,
-# plus a single fire at 00:00 — 20 fires/day, every hour except 01-04.
-# Crons evaluate in UTC; UTC+7 hours {00, 05..23} map to UTC {17, 22-23, 0-16}.
-[triggers]
-crons = [
-  "0 0-17,22-23 * * *", # UTC+7: 00:00 + 05:00..23:00 hourly
-]
+#
+# DISABLED: this worker is parked. I migrated this routine to cron-job.org
+# to keep my CF cron-trigger quota free for other workers (see README).
+# To re-enable, uncomment the block below and `npx wrangler deploy`.
+#
+# [triggers]
+# crons = [
+#   "0 0-17,22-23 * * *", # UTC+7: 00:00 + 05:00..23:00 hourly
+# ]
 
 # Workers Logs / traces. `head_sampling_rate = 1` keeps 100% of invocations
 # (low volume here — ~20/day — so full retention is free). Drop to e.g. 0.1