feat(server): auto-resolve Sentinel URL and polish setup UI

Ensure a Sentinel endpoint from instance FQDN/IP when enabling, use process dialogs for validation with install state, and tidy server create, boarding, metrics empty state, and log timestamps.

tests/Feature/ServerMetricsEmptyStateTest.php

@@ -0,0 +1,10 @@
+<?php
+
+test('sentinel-required metrics state does not repeat an unavailable badge', function () {
+    $view = file_get_contents(resource_path('views/livewire/server/charts.blade.php'));
+    $sentinelRequiredState = str($view)->after('@else')->before('@endif')->toString();
+
+    expect($sentinelRequiredState)
+        ->toContain('title="Sentinel is required"')
+        ->not->toContain('status="Unavailable"');
+});