feat: make ServerMetricsService optional in PrometheusController

Make ServerMetricsService dependency optional to handle cases where
the Gophpeek\SystemMetrics package is not installed. The Prometheus
endpoint will work without server metrics, exporting only queue metrics.

Note: Server metrics require gophpeek/system-metrics package.
When not available, Prometheus export continues with queue metrics only.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: sylvesterdamgaard

.claude/settings.local.json

@@ -42,7 +42,8 @@
       "Bash(curl:*)",
       "Bash(/Users/sylvester/Library/Application\\ Support/Herd/bin/php:*)",
       "Bash(/Users/sylvester/Library/Application Support/Herd/bin/php:*)",
-      "Bash(composer dump-autoload:*)"
+      "Bash(composer dump-autoload:*)",
+      "Bash(timeout 10 php:*)"
     ],
     "deny": [],
     "ask": []

src/Http/Controllers/PrometheusController.php

@@ -18,7 +18,7 @@
     public function __construct(
         private MetricsQueryService $metricsQuery,
         private QueueMetricsConfig $config,
-        private ServerMetricsService $serverMetrics,
+        private ?ServerMetricsService $serverMetrics = null,
     ) {}
 
     public function __invoke(): Response
@@ -68,8 +68,16 @@ public function __invoke(): Response
             'Overall health score (0-100)'
         );
 
-        // Server resource metrics
-        $serverMetrics = $this->serverMetrics->getCurrentMetrics();
+        // Server resource metrics (only if ServerMetricsService is available)
+        if ($this->serverMetrics !== null) {
+            try {
+                $serverMetrics = $this->serverMetrics->getCurrentMetrics();
+            } catch (\Throwable $e) {
+                $serverMetrics = ['available' => false];
+            }
+        } else {
+            $serverMetrics = ['available' => false];
+        }
 
         if ($serverMetrics['available']) {
             // Type-safe extraction with proper PHPDoc syntax for string keys