Add ping endpoint, update-refresh prompt, and dark-mode polish

tests/Feature/PingControllerTest.php

@@ -0,0 +1,18 @@
+<?php
+
+use App\Models\Setting;
+
+it('returns ping status with build and notification state', function (): void {
+    Setting::updateOrCreate(['key' => 'build'], ['value' => '1337']);
+
+    $response = $this->getJson('/ping');
+
+    $response->assertOk();
+    $response->assertJson([
+        'connect' => 'ok',
+        'version_status' => [
+            'build' => 1337,
+        ],
+        'notification_state' => false,
+    ]);
+});