Demo baseline reset: full DB snapshot/restore (v2.3.0)

Hourly reset now restores entire DB from baseline snapshot instead of
just deleting demo trips. This reverts ALL demo user changes including
modifications to shared admin trips. Admin credentials (password, API
keys) are preserved across resets. Admin can save new baseline via
Admin Panel button. Removed demoWriteBlock middleware.

server/src/routes/admin.js

@@ -110,4 +110,18 @@ router.get('/stats', (req, res) => {
   res.json({ totalUsers, totalTrips, totalPlaces, totalPhotos, totalFiles });
 });
 
+// POST /api/admin/save-demo-baseline (demo mode only)
+router.post('/save-demo-baseline', (req, res) => {
+  if (process.env.DEMO_MODE !== 'true') {
+    return res.status(404).json({ error: 'Not found' });
+  }
+  try {
+    const { saveBaseline } = require('../demo/demo-reset');
+    saveBaseline();
+    res.json({ success: true, message: 'Demo baseline saved. Hourly resets will restore to this state.' });
+  } catch (err) {
+    res.status(500).json({ error: 'Failed to save baseline: ' + err.message });
+  }
+});
+
 module.exports = router;