fix: add username/icon_url to Forgejo Discord webhook config

Prevents the 'meta json: readObjectStart' error on fresh deploys.
Existing hooks already fixed via direct DB update.

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

roles/services/tasks/main.yml

@@ -105,6 +105,8 @@
       config:
         url: "{{ discord_webhook_deploys }}"
         content_type: "json"
+        username: "Forgejo"
+        icon_url: ""
       events: ["push", "create"]
       active: true
     status_code: 201