feat: wire the latest-chapter poller into startup

Five env vars, all with defaults sized for this deployment (84 series
at a 1h cadence). Bad values log and fall back rather than failing
startup, and the cooldown is floored at 15m. Fetches go through
tls-client with a Chrome profile as defence in depth.

.env.example

@@ -29,3 +29,22 @@ WEB_PASSWORD=
 # publish the UI router on a domain you do not own. The same container also
 # answers on MANGA_API_HOST for the userscript's API.
 # MANGA_WEB_HOST=manga.example.com
+
+# --- Latest-chapter poller ---
+# The backend re-checks each bookmarked series' newest published chapter on its
+# own schedule, so latest_chapter stays fresh even when you never open the manga
+# sites. This runs in parallel with the userscript's own in-browser check.
+# Set to 0 to turn it off entirely.
+# LATEST_CHAPTER_POLL_ENABLED=1
+#
+# Two independent clocks. COOLDOWN is how long one series rests between checks;
+# INTERVAL is how often the poller wakes up and looks for series past that
+# cooldown. Shortening INTERVAL cannot shorten a COOLDOWN.
+# LATEST_CHAPTER_POLL_COOLDOWN=1h     # per series, floor 15m
+# LATEST_CHAPTER_POLL_INTERVAL=10m    # how often to wake
+# LATEST_CHAPTER_POLL_BATCH=14        # series per wake
+# LATEST_CHAPTER_POLL_STAGGER=20s     # delay between fetches in a batch
+#
+# BATCH x (COOLDOWN / INTERVAL) series hold the cooldown cadence — 84 with these
+# defaults. Beyond that the cadence stretches uniformly rather than breaking;
+# raise BATCH or lower INTERVAL. Keep BATCH x STAGGER under INTERVAL.