fix: support query parameter-based secret validation fallback to fix Ombi webhooks (#47)

ARCHITECTURE.md

@@ -393,9 +393,9 @@ POST /api/webhook/ombi
 Both endpoints share identical processing logic:
 
 ```
-Sonarr/Radarr
+Sonarr/Radarr/Ombi
     POST /api/webhook/sonarr
-    Headers: X-Sofarr-Webhook-Secret: <secret>
+    Headers: X-Sofarr-Webhook-Secret: <secret> OR URL parameter: ?secret=<secret>
     Body:    { "eventType": "Grab", "instanceName": "Main Sonarr",
                "date": "2026-05-19T10:00:00.000Z", … }
         │
@@ -404,6 +404,7 @@ Sonarr/Radarr
         │
         ▼
     validateWebhookSecret()  ──fail──► 401 Unauthorized
+        (Checks header or query param)
         │ ok
         ▼
     validatePayload()        ──fail──► 400 Bad Request