Refactor: reorganise namespaces and move service DTOs to Models/Contracts

- Move Client/Http, Services, Parsers under Infrastructure/ (Client, Services, Parsers)
- Move config helpers (DnsmasqConfKeys, DnsmasqOptionTooltips, DnsmasqFileEncoding, EffectiveConfigFieldBuilder) to Infrastructure/Helpers/Config; ApiJsonOptions to Helpers/Http
- Move Configuration types (ApplicationOptions, DnsmasqOptions, DnsmasqOptionsValidator) to Models/Config
- Merge Models/Status and Models/EffectiveConfig into Models/Dnsmasq and Models/Dnsmasq/EffectiveConfig
- Move Client/Models and Client/Services to Models/Client and Infrastructure/Services
- Move ConfigSetSnapshot, HostsSnapshot, ProcessRunResult, ManagedConfigContent from Infrastructure/Services/Abstractions to Models/Contracts
- Update all namespaces and usings; tests pass

src/DnsmasqWebUI/Infrastructure/Services/ReloadService.cs

@@ -0,0 +1,65 @@
+using DnsmasqWebUI.Models.Config;
+using DnsmasqWebUI.Infrastructure.Services.Abstractions;
+using Microsoft.Extensions.Options;
+
+namespace DnsmasqWebUI.Infrastructure.Services;
+
+public class ReloadService : IReloadService
+{
+    private readonly DnsmasqOptions _options;
+    private readonly IProcessRunner _processRunner;
+    private readonly ILogger<ReloadService> _logger;
+    private readonly SemaphoreSlim _reloadLock = new(1, 1);
+
+    public ReloadService(IProcessRunner processRunner, IOptions<DnsmasqOptions> options, ILogger<ReloadService> logger)
+    {
+        _processRunner = processRunner;
+        _options = options.Value;
+        _logger = logger;
+    }
+
+    public async Task<ReloadResult> ReloadAsync(CancellationToken ct = default)
+    {
+        if (string.IsNullOrWhiteSpace(_options.ReloadCommand))
+        {
+            _logger.LogDebug("Reload command not configured");
+            return new ReloadResult(true, 0, null, "Reload command not configured");
+        }
+
+        if (!await _reloadLock.WaitAsync(TimeSpan.Zero, ct))
+        {
+            _logger.LogDebug("Reload already in progress, rejecting concurrent request");
+            return new ReloadResult(false, -1, null, "Reload already in progress.");
+        }
+
+        try
+        {
+            var result = await _processRunner.RunAsync(_options.ReloadCommand, TimeSpan.FromSeconds(30), ct);
+            var stderr = result.Stderr;
+            if (result.TimedOut)
+                stderr = (string.IsNullOrEmpty(stderr) ? "" : stderr + "\n") + "Reload command timed out after 30 seconds.";
+            if (result.ExceptionMessage != null)
+                stderr = (string.IsNullOrEmpty(stderr) ? "" : stderr + "\n") + result.ExceptionMessage;
+
+            if (result.ExitCode != 0 && result.ExitCode.HasValue)
+                _logger.LogWarning("Reload command exited with {ExitCode}: {Stderr}", result.ExitCode.Value, stderr);
+            else if (result.ExitCode == 0)
+                _logger.LogInformation("Reload command succeeded");
+
+            return new ReloadResult(
+                result.ExitCode == 0,
+                result.ExitCode ?? -1,
+                result.Stdout,
+                stderr);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to run reload command");
+            return new ReloadResult(false, -1, null, ex.Message);
+        }
+        finally
+        {
+            _reloadLock.Release();
+        }
+    }
+}