fix: address final-review findings on the latest-chapter poller

Wires the five poll env vars into docker-compose (the documented kill
switch was inert), skips fetching unknown sites and non-https URLs
before spending a request, and makes runOnce's summary log fire on
empty and cancelled ticks. Records the accepted non-atomic Get+Upsert
window and the one-interval startup delay in the docs.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docker-compose.yml

@@ -20,6 +20,13 @@ services:
       PORT: "8080"
       # Gates the browser UI. Unset means the web routes are not served at all.
       WEB_PASSWORD: ${WEB_PASSWORD:-}
+      # Latest-chapter poller. LATEST_CHAPTER_POLL_ENABLED=0 in .env is the kill
+      # switch; it only takes effect because these are listed here.
+      LATEST_CHAPTER_POLL_ENABLED: ${LATEST_CHAPTER_POLL_ENABLED:-1}
+      LATEST_CHAPTER_POLL_COOLDOWN: ${LATEST_CHAPTER_POLL_COOLDOWN:-1h}
+      LATEST_CHAPTER_POLL_INTERVAL: ${LATEST_CHAPTER_POLL_INTERVAL:-10m}
+      LATEST_CHAPTER_POLL_BATCH: ${LATEST_CHAPTER_POLL_BATCH:-14}
+      LATEST_CHAPTER_POLL_STAGGER: ${LATEST_CHAPTER_POLL_STAGGER:-20s}
     volumes:
       - bookmarks-data:/data
     # Bound to loopback only: the proxy (or curl during smoke test) reaches it,