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>

src/Http/Controllers/WebhookController.php

@@ -87,11 +87,17 @@ class WebhookController extends Controller
 
     private function fireTest(string $url, ?string $secret)
     {
-        $payload = [
+        $message = '✅ Test webhook from ' . config('app.name') . ' — endpoint is reachable.';
+        $genericPayload = [
             'event'     => 'test',
             'timestamp' => now()->toIso8601String(),
-            'data'      => ['message' => 'This is a test webhook from ' . config('app.name')],
+            'message'   => $message,
+            'data'      => ['message' => $message],
         ];
+        // Shape the payload to match the target platform (Google Chat,
+        // Slack, Discord, Teams) so the test exercises the same code
+        // path real events use.
+        $payload = \Dashboard\Unifi\Services\WebhookCheckService::buildPlatformPayload($url, $message, $genericPayload);
 
         $headers = ['Content-Type' => 'application/json'];
         if ($secret) {