Add 'All' history range to the dashboard and pressure tendency chart

- /api/station/history?range=all returns everything on disk, bucketed (cached 60s)
- Year-aware axis labels for 1y/2y/3y/All
- Pressure tendency widens its change window to the bucket size on long ranges and says so

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

app/server.js

@@ -1475,13 +1475,37 @@ function bucketReadings(readings, points) {
 app.get('/api/station/history', requireDashboardAuth, (req, res) => {
   const rangeMap = { '1h': 3600000, '6h': 21600000, '24h': 86400000, '2d': 172800000, '7d': 604800000, '30d': 2592000000, '90d': 7776000000, '1y': 31536000000, '2y': 63072000000, '3y': 94608000000 };
   const range = req.query.range || '24h';
+  const points = parseInt(req.query.points);
+
+  if (range === 'all') {
+    // Everything on disk, always bucketed (default 720 points) so the payload stays small
+    const first = firstStationDay();
+    if (!first) return res.json([]);
+    const rangeAll = Date.now() - Date.parse(first + 'T00:00:00Z') + 2 * 86400000;
+    const pts = points >= 50 ? points : 720;
+    const key = `${first}|${pts}`;
+    if (allHistoryCache.key === key && Date.now() - allHistoryCache.at < 60000) return res.json(allHistoryCache.data);
+    const readingsAll = loadStationReadings(rangeAll);
+    const data = readingsAll.length > pts ? bucketReadings(readingsAll, pts) : readingsAll;
+    allHistoryCache = { key, at: Date.now(), data };
+    return res.json(data);
+  }
+
   const rangeMs = rangeMap[range] || rangeMap['24h'];
   const readings = loadStationReadings(rangeMs);
-  const points = parseInt(req.query.points);
   if (points >= 50 && readings.length > points) return res.json(bucketReadings(readings, points));
   res.json(readings);
 });
 
+// Earliest day with saved readings (YYYY-MM-DD, UTC file name)
+let allHistoryCache = { key: null, at: 0, data: null };
+function firstStationDay() {
+  try {
+    const files = fs.readdirSync(STATION_DIR).filter(f => /^\d{4}-\d{2}-\d{2}\.jsonl$/.test(f)).sort();
+    return files.length ? files[0].slice(0, 10) : null;
+  } catch { return null; }
+}
+
 // Latest station reading
 app.get('/api/station/latest', requireDashboardAuth, async (req, res) => {
   if (!ambientServerConfig.apiKey || !ambientServerConfig.appKey) {