fix(api): expose nested server secrets for privileged tokens

Add `exposeNestedServerSecrets()` to Applications, Databases, and
Services controllers so that `read:sensitive`/`root` tokens see
sentinel and logdrain fields on eager-loaded Server + ServerSetting
relations.

ServicesController handles both single models and Eloquent Collections
(listing endpoint passes a Collection per project).

Tests tightened to use JSON-key assertions (`"field":`) to avoid false
positives from field names appearing in values.

app/Http/Controllers/Api/ApplicationsController.php

@@ -57,6 +57,7 @@ class ApplicationsController extends Controller
                 'value',
                 'real_value',
             ]);
+            $this->exposeNestedServerSecrets($application);
         } else {
             $application->makeHidden([
                 'private_key_id',
@@ -66,6 +67,34 @@ class ApplicationsController extends Controller
         return serializeApiResponse($application);
     }
 
+    /**
+     * Expose sensitive fields on eager-loaded nested Server + ServerSetting
+     * relations for callers with the `read:sensitive` or `root` token ability.
+     * Models hide these by default via $hidden; this re-exposes them per-request.
+     */
+    private function exposeNestedServerSecrets($model): void
+    {
+        $server = $model->destination?->server ?? null;
+        if (! $server) {
+            return;
+        }
+        $server->makeVisible([
+            'logdrain_axiom_api_key',
+            'logdrain_newrelic_license_key',
+        ]);
+        $settings = $server->settings ?? null;
+        if ($settings) {
+            $settings->makeVisible([
+                'sentinel_token',
+                'sentinel_custom_url',
+                'logdrain_newrelic_license_key',
+                'logdrain_axiom_api_key',
+                'logdrain_custom_config',
+                'logdrain_custom_config_parser',
+            ]);
+        }
+    }
+
     #[OA\Get(
         summary: 'List',
         description: 'List all applications.',