Added small system overview

Moonlight.Api/Http/Controllers/Admin/SystemController.cs

@@ -0,0 +1,33 @@
+using Microsoft.AspNetCore.Mvc;
+using Moonlight.Api.Services;
+using Moonlight.Shared.Http.Responses.Admin;
+
+namespace Moonlight.Api.Http.Controllers.Admin;
+
+[ApiController]
+[Route("api/admin/system")]
+public class SystemController : Controller
+{
+    private readonly ApplicationService ApplicationService;
+
+    public SystemController(ApplicationService applicationService)
+    {
+        ApplicationService = applicationService;
+    }
+
+    [HttpGet("info")]
+    public async Task<ActionResult<SystemInfoResponse>> GetInfoAsync()
+    {
+        var cpuUsage = await ApplicationService.GetCpuUsageAsync();
+        var memoryUsage = await ApplicationService.GetMemoryUsageAsync();
+
+        return new SystemInfoResponse(
+            cpuUsage,
+            memoryUsage,
+            ApplicationService.OperatingSystem,
+            DateTimeOffset.UtcNow - ApplicationService.StartedAt,
+            ApplicationService.VersionName,
+            ApplicationService.IsUpToDate
+        );
+    }
+}