fix(webhooks): test endpoint formats payload per platform; add missing column

* The Test URL button was POSTing a generic {event, timestamp, data}
  envelope to every endpoint. Google Chat / Slack / Discord / Teams
  reject anything that isn't their specific shape — so a successful
  Laravel request still got a 400 back from the platform, making the
  test look broken. The real webhook events already handle this via
  WebhookCheckService::formatPayloadForPlatform; that helper is now
  exposed as a public static (buildPlatformPayload) and the test
  endpoint uses the same code path, so the test exercises the same
  format real events will.
* unifi_device_states was missing a consecutive_count column the
  WebhookCheckService inserts on every snapshot capture. The scheduler
  was throwing "Unknown column 'consecutive_count'" once a minute.
  Added an idempotent migration.

v1.6.1.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

composer.json

@@ -1,7 +1,7 @@
 {
     "name": "dashboard/unifi",
     "description": "UniFi network management, WiFi stats, and captive portal authentication for the Dashboard platform",
-    "version": "1.6.0",
+    "version": "1.6.1",
     "type": "library",
     "license": "MIT",
     "autoload": {