feat: initial commit — UniFi snap-in package

Full UniFi dashboard snap-in including:
- WiFi/client/device stats with time-series snapshots
- Client Dashboard with traffic, satisfaction, signal, download charts
- Webhook alerting with debounced offline/online detection
- AP snapshot collection, client snapshot collection
- Device classification (type and OS) from OUI/hostname heuristics
- Webhook cooldown, templates, and multi-platform delivery

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

config/unifi.php

@@ -0,0 +1,12 @@
+<?php
+
+return [
+    // Polling intervals (seconds) for the stats cache
+    'cache_ttl_devices'  => 30,
+    'cache_ttl_clients'  => 15,
+    'cache_ttl_health'   => 10,
+    'cache_ttl_events'   => 30,
+
+    // Maximum portal session duration defaults (overridden per-group in DB)
+    'portal_session_default_minutes' => 720, // 12 hours
+];