Add --no-html flag and Synology Task Scheduler setup

--no-html skips dashboard generation for deployments where river.php
reads the SQLite DB directly. synology-task.sh is a ready-to-configure
wrapper for DSM Task Scheduler.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

synology-task.sh

@@ -0,0 +1,21 @@
+#!/bin/sh
+# River monitor poller — run this via Synology Task Scheduler every 15 minutes.
+#
+# Setup:
+#   1. Copy river_monitor.py to your Synology (e.g. /volume1/homes/simon/river_monitor.py)
+#   2. Set WEB_DATA_DIR below to the data/ folder inside your web repo on the Synology
+#   3. In DSM: Control Panel → Task Scheduler → Create → Scheduled Task → User-defined script
+#      - User: your DSM user (needs write access to WEB_DATA_DIR)
+#      - Schedule: every 15 minutes
+#      - Task: sh /volume1/homes/simon/synology-task.sh
+#   4. Run once manually with --backfill to populate history, then let the schedule take over
+
+SCRIPT=/volume1/homes/simon/river_monitor.py
+WEB_DATA_DIR=/volume1/web/data
+DB=$WEB_DATA_DIR/river_levels.db
+LOG=$WEB_DATA_DIR/river-monitor.log
+
+/usr/bin/python3 "$SCRIPT" \
+    --db "$DB" \
+    --no-html \
+    >> "$LOG" 2>&1