Enrich alarms with device names for Loki logs

Added device name enrichment to alarms so that Loki logs show
human-readable device names instead of just MAC addresses.

Changes:
- Modified collectAlarms to fetch devices and build MAC-to-name lookup
- Added extractDeviceNameFromAlarm helper to extract MAC addresses from
  alarm messages and lookup corresponding device names
- Device names are extracted from messages like "AP[fc:ec:da:89:a6:91]"
  or from SrcMAC/DstMAC fields
- Added go.mod replace directive to use local unifi library with new
  DeviceName field

The device_name field will now be included in the JSON output sent to
Loki, making it easier to identify which device triggered an alarm.

Fixes #415

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

go.mod

@@ -46,3 +46,5 @@ require (
 	golang.org/x/sys v0.40.0 // indirect
 	google.golang.org/protobuf v1.36.11 // indirect
 )
+
+replace github.com/unpoller/unifi/v5 => ../unifi