feat(claude-do): UI-Prozess loggt auf Platte (ui-.log) + fehlgeschlagene Hub-

## Problem
Beim DeleteTask-Bug (Fix 352aaa52) gab es null Spuren: Der UI-Prozess (ClaudeDo.App) hat gar kein File-Logging (weder Serilog noch `Microsoft.Extensions.Logging` sind in App/Ui referenziert), und im Worker loggt SignalR fehlgeschlagene Hub-Invocations nur auf Debug (`Microsoft.AspNetCore` steht in `src/ClaudeDo.Worker/Program.cs` Z. 60 auf Warning). Die Ursache ließ sich nur finden, ind

ClaudeDo-Task: d2ae3831-733f-4d40-93d7-70c93da11590

src/ClaudeDo.App/Program.cs

@@ -13,6 +13,7 @@ using ClaudeDo.Ui.ViewModels.Modals;
 using ClaudeDo.Ui.ViewModels.Modals.Settings;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.DependencyInjection;
+using Serilog;
 using System;
 using System.Globalization;
 using System.IO;
@@ -20,6 +21,7 @@ using System.Linq;
 using System.Net.Http;
 using System.Reflection;
 using System.Runtime.InteropServices;
+using System.Threading.Tasks;
 
 namespace ClaudeDo.App;
 
@@ -34,6 +36,35 @@ sealed class Program
         if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
             SetCurrentProcessExplicitAppUserModelID("ClaudeDo.App");
 
+        var logRoot = Path.Combine(Paths.AppDataRoot(), "logs");
+        Directory.CreateDirectory(logRoot);
+        Log.Logger = new LoggerConfiguration()
+            .MinimumLevel.Information()
+            .WriteTo.File(
+                Path.Combine(logRoot, "ui-.log"),
+                rollingInterval: RollingInterval.Day,
+                retainedFileCountLimit: 7,
+                shared: true)
+            .CreateLogger();
+
+        var version = Assembly.GetEntryAssembly()?
+            .GetCustomAttribute<AssemblyInformationalVersionAttribute>()?.InformationalVersion
+            ?? "0.0.0";
+        Log.Information("ClaudeDo.App starting (version: {Version})", version);
+
+        // Last-resort net: any exception that misses every other handler still gets one
+        // Fatal line in the log before the process dies.
+        AppDomain.CurrentDomain.UnhandledException += (_, e) =>
+        {
+            Log.Fatal(e.ExceptionObject as Exception, "Unhandled exception, terminating (IsTerminating: {IsTerminating})", e.IsTerminating);
+            Log.CloseAndFlush();
+        };
+        TaskScheduler.UnobservedTaskException += (_, e) =>
+        {
+            Log.Error(e.Exception, "Unobserved task exception");
+            e.SetObserved();
+        };
+
         var services = BuildServices();
 
         using (var scope = services.CreateScope())
@@ -62,6 +93,8 @@ sealed class Program
             {
                 /* best effort on shutdown */
             }
+
+            Log.CloseAndFlush();
         }
     }