feat(profile): add uploadable avatars with local/S3 storage

Users can upload and remove profile pictures on the profile page.
Admins choose local or instance S3 storage in advanced settings.
Avatars are compressed to JPEG and served via a private cached route.

app/Models/InstanceSettings.php

@@ -49,6 +49,8 @@ class InstanceSettings extends Model
         'is_mcp_server_enabled',
         'webhook_allowed_internal_hosts',
         'webhook_allow_localhost',
+        'avatar_storage_type',
+        'avatar_s3_storage_id',
     ];
 
     protected $hidden = [