Same tick previously fired every due watch back-to-back (burst of N requests,
worst right after a restart when all watches are due at once). Now each watch
URL fetch is followed by a pause of FETCH_GAP_SECONDS (float, default 1, env
tunable; 0 disables) on both success and failure paths.
Also thread kw_fk_col into load_ignored_keywords() inside
send_pending_notifications() so the physical-FK lookup (445040a) actually takes
effect instead of silently falling back to the watch Link column.
The search_url Lookup column is redundant: the watch Link -> Settings row
already defines the association. Remove handling for the column:
- _ensure_keyword_watch_link() no longer creates a Lookup; deletes any
legacy search_url (URL or Lookup type) on bootstrap
- load_ignored_keywords(kw_tid, settings_tid) resolves Settings.url via
the watch link, one Settings fetch per cycle (no N+1)
- send_pending_notifications passes settings_tid through
- Add COMPOSE-SETUP.md: detail documentation for the compose stack
(topology, compose block-by-block, Dockerfile, healthcheck, deploy paths,
troubleshooting); referenced from README + DOCUMENTATION.md
hoelee