Add CLAUDE.md with web integration instructions for river.php

Documents the DB schema, useful queries, and exact steps for the
web repo Claude to add river.php and the nav link to the site.

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

CLAUDE.md

@@ -0,0 +1,56 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code when working with this repository.
+
+## Project Overview
+
+`river_monitor.py` polls the UK Environment Agency's real-time flood-monitoring API for river level stations within a configurable radius, archives readings to a local SQLite database, and optionally generates a self-contained HTML dashboard.
+
+## Synology / Website Integration
+
+The primary deployment target is a Synology NAS running Web Station, alongside the `simon/web` Gitea repo (theatari.com). The poller runs via DSM Task Scheduler (`synology-task.sh`) every 15 minutes with `--no-html`, writing only to the SQLite database. A `river.php` page in the web repo reads the DB and renders the dashboard as part of the site.
+
+### Database
+
+The DB is written to `data/river_levels.db` inside the web repo on the Synology (path configured in `synology-task.sh`). That directory is already shielded from direct web access by `data/.htaccess`.
+
+**Schema:**
+
+```
+stations: station_id TEXT PK, label TEXT, river_name TEXT, lat REAL, lon REAL
+
+readings: id INTEGER PK, station_id TEXT, measure_id TEXT, unit TEXT,
+          qualifier TEXT, value REAL, date_time TEXT, fetched_at TEXT
+          UNIQUE(measure_id, date_time)
+```
+
+**Useful query — latest reading per station:**
+
+```sql
+SELECT s.label, s.river_name, r.value, r.unit, r.date_time
+FROM stations s
+JOIN readings r ON r.station_id = s.station_id
+WHERE r.date_time = (
+    SELECT MAX(date_time) FROM readings WHERE station_id = s.station_id
+)
+ORDER BY s.label;
+```
+
+**Useful query — recent history for sparklines (last 50 readings per station):**
+
+```sql
+SELECT station_id, value, date_time
+FROM readings
+WHERE station_id = ?
+ORDER BY date_time DESC
+LIMIT 50;
+```
+
+### Instructions for the web repo Claude
+
+When adding the river page to `simon/web`:
+
+- Create `river.php` following the same structure as `blog.php`: open the DB with `new SQLite3('data/river_levels.db', SQLITE3_OPEN_READONLY)`, include `includes/header.php` and `includes/footer.php`, and render using existing CSS classes and custom property variables (never hardcode colours).
+- Add a "River" nav link in **all 6 nav locations**: `index.html`, `links.html`, `gifs.html`, `games.html`, `contact.html`, and `includes/header.php`. Mark it active in `river.php` the same way blog pages mark the Blog link active via `blog_nav_active()`.
+- The page should show current level + a small trend sparkline per station, consistent with the existing card/grid style.
+- Chart.js (already used in the standalone dashboard) can be loaded from CDN the same way other external scripts are used on the site.