Dynamic resolved count, host search filter, lt-divider for UniFi section

- db.py: add resolved_24h to get_status_summary() so each /api/status
  poll carries the fresh 24h resolved count
- app.js: wire stat-resolved-val to update from summary.resolved_24h
  so the Resolved 24h card stays accurate after auto-refresh
- index.html: add lt-toolbar/lt-search above host grid for quick
  client-side host filtering by name
- links.html: replace custom unifi-section-header div with lt-divider
- style.css: remove unused .unifi-section-header rules

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

db.py

@@ -222,10 +222,17 @@ def get_status_summary() -> dict:
                    WHERE resolved_at IS NULL GROUP BY severity"""
             )
             counts = {r['severity']: r['cnt'] for r in cur.fetchall()}
+            cur.execute(
+                """SELECT COUNT(*) as cnt FROM network_events
+                   WHERE resolved_at IS NOT NULL
+                   AND resolved_at > DATE_SUB(NOW(), INTERVAL 24 HOUR)"""
+            )
+            resolved_24h = cur.fetchone()['cnt']
             return {
                 'critical': counts.get('critical', 0),
                 'warning': counts.get('warning', 0),
                 'info': counts.get('info', 0),
+                'resolved_24h': resolved_24h,
             }