<Feat>: Add universal NLog diagnostics and improve AppDiagnostic UI

Cause:

- Live diagnostics required logging from multiple applications without blocking TBF.
- Shared nlog.config files caused configuration conflicts.
- The original viewer lacked configurable colors and practical log controls.
- Inconsistent diagnostic deployment caused log transfer failures and locked shared DLLs during builds.

Solution:

1. Added universal diagnostic transport
   - Added AppDiagnostic.Logging with an NLog target and named-pipe communication.
   - Added background buffering and automatic reconnection.
   - Registered the diagnostic connector programmatically.

2. Separated diagnostic window lifecycle
   - Run AppDiagnostic as an independent process.
   - Activate the existing window on repeated launches.
   - Keep TBF running when the diagnostic window closes.

3. Corrected diagnostic deployment
   - Copy the complete diagnostic output into a dedicated AppDiagnostic subdirectory during build.
   - Overwrite existing deployment files to prevent inconsistent versions.
   - Validate and launch the executable from that subdirectory with an explicit working directory.

4. Improved the log viewer
   - Added configurable substring colors with a palette and live preview.
   - Added text, level and application filters.
   - Added line wrapping, clipboard actions and log export.
   - Added Pause/Resume, Refresh, Clear, auto-scroll and Always on top.
   - Added connection and log counters.
   - Persist color rules between sessions.

5. Removed legacy dependencies
   - Replaced LiveLogCache with structured diagnostic storage.
   - Removed AppDiagnostic dependencies on log4net and SharedComponents.

Validation:

- Confirmed successful log transfer when launching AppDiagnostic from TBF.

AppDiagnostic/Program.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 using System.Windows.Forms;
 
@@ -14,9 +15,26 @@ namespace AppDiagnostic
         [STAThread]
         static void Main()
         {
-            Application.EnableVisualStyles();
-            Application.SetCompatibleTextRenderingDefault(false);
-            Application.Run(new MainForm());
+            bool isFirstInstance;
+
+            using (var instanceMutex = new Mutex(true, "Sensus.AppDiagnostic.SingleInstance", out isFirstInstance))
+            using (var activationEvent = new EventWaitHandle(false, EventResetMode.AutoReset, "Sensus.AppDiagnostic.Activate"))
+            {
+                if (!isFirstInstance)
+                {
+                    activationEvent.Set();
+                    return;
+                }
+
+                Application.EnableVisualStyles();
+                Application.SetCompatibleTextRenderingDefault(false);
+
+                using (var diagnosticServer = new DiagnosticPipeServer(DiagnosticLogStore.Instance.Add))
+                {
+                    diagnosticServer.Start();
+                    Application.Run(new MainForm(() => diagnosticServer.ConnectedClientCount, () => activationEvent.WaitOne(0)));
+                }
+            }
         }
     }
 }