App logs: add Refresh and Download logs buttons; add api/logging/logs/download endpoint

src/DnsmasqWebUI/Components/Dnsmasq/AppLogs/AppLogsSection.razor

@@ -31,3 +31,7 @@
 </p>
 <AppLogsFiltersModal IsVisible="_filtersModalVisible" OnClose="CloseFiltersModal" />
 <LogsPreView Id="app-logs-pre" Placeholder="@_initialPlaceholder" Freeze="_logsContentReceived" />
+<div class="mt-2 d-flex flex-wrap gap-2 align-items-center">
+    <button class="btn btn-primary btn-sm" @onclick="RequestRefreshAsync" disabled="@_refreshing"><i class="bi bi-arrow-repeat me-1" aria-hidden="true"></i>Refresh</button>
+    <a href="api/logging/logs/download" download="app.log" class="btn btn-primary btn-sm"><i class="bi bi-download me-1" aria-hidden="true"></i>Download logs</a>
+</div>

src/DnsmasqWebUI/Components/Dnsmasq/AppLogs/AppLogsSection.razor.cs

@@ -19,6 +19,7 @@ public partial class AppLogsSection : IAsyncDisposable
 
     private bool _justUpdated;
     private bool _logsContentReceived;
+    private bool _refreshing;
     private int _intervalSeconds;
     private string _logLevel = "Information";
     private bool _logLevelDisabled;
@@ -91,6 +92,25 @@ public partial class AppLogsSection : IAsyncDisposable
     private void OpenFiltersModal() => _filtersModalVisible = true;
     private void CloseFiltersModal() => _filtersModalVisible = false;
 
+    private async Task RequestRefreshAsync()
+    {
+        if (_hubConnection?.State != HubConnectionState.Connected)
+            return;
+        _refreshing = true;
+        StateHasChanged();
+        try
+        {
+            await _hubConnection.InvokeAsync("RequestAppLogsSnapshot", _cts.Token);
+        }
+        catch (OperationCanceledException) { }
+        catch (Exception) { /* ignore */ }
+        finally
+        {
+            _refreshing = false;
+            StateHasChanged();
+        }
+    }
+
     private async Task OnLogLevelChanged()
     {
         if (string.IsNullOrEmpty(_logLevel)) return;

src/DnsmasqWebUI/Controllers/LoggingController.cs

@@ -1,6 +1,8 @@
+using System.Text;
 using System.Text.Json;
 using System.Text.Json.Nodes;
 using DnsmasqWebUI.Infrastructure.Logging;
+using DnsmasqWebUI.Infrastructure.Services.Logs.Abstractions;
 using DnsmasqWebUI.Models.Config;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.Extensions.Configuration;
@@ -12,22 +14,39 @@ namespace DnsmasqWebUI.Controllers;
 [Route("api/[controller]")]
 public class LoggingController : ControllerBase
 {
+    private const int AppLogsDownloadMaxLines = 5000;
+
     private readonly IConfiguration _configuration;
     private readonly IConfigurationRoot _configurationRoot;
     private readonly RuntimeOverridesOptions _overridesOptions;
+    private readonly IAppLogsBuffer _appLogsBuffer;
     private readonly ILogger<LoggingController> _logger;
 
     public LoggingController(
         IConfiguration configuration,
         IOptions<RuntimeOverridesOptions> overridesOptions,
+        IAppLogsBuffer appLogsBuffer,
         ILogger<LoggingController> logger)
     {
         _configuration = configuration;
         _configurationRoot = (IConfigurationRoot)configuration;
         _overridesOptions = overridesOptions.Value;
+        _appLogsBuffer = appLogsBuffer;
         _logger = logger;
     }
 
+    /// <summary>Download recent app logs from the in-memory buffer (up to AppLogsDownloadMaxLines).</summary>
+    [HttpGet("logs/download")]
+    public IActionResult GetAppLogsDownload()
+    {
+        var lines = _appLogsBuffer.GetRecent(maxLines: AppLogsDownloadMaxLines);
+        var content = string.Join(Environment.NewLine, lines);
+        if (lines.Count > 0 && !content.EndsWith(Environment.NewLine))
+            content += Environment.NewLine;
+        _logger.LogDebug("App logs download, lines={Count}", lines.Count);
+        return File(Encoding.UTF8.GetBytes(content), "text/plain", "app.log");
+    }
+
     /// <summary>Get the current minimum log level from configuration (Logging:LogLevel:Default).</summary>
     [HttpGet("level")]
     public ActionResult<LogLevelResponse> GetLevel()