Migrate legacy VB.NET service to modern C# Worker

Migrated the legacy VB.NET Windows Service to a modern C# Worker Service targeting .NET Framework 4.6.2. Key changes include:

- Added `Microsoft.Extensions.Hosting.WindowsServices`, `NLog`, and `Quartz` for logging and scheduling.
- Introduced `LogConfigFactory` to bridge `ServiceConfig` and `LogConfig` for Quartz jobs.
- Rewrote `Worker` to handle the full service lifecycle, including database connection, temp file management, and scheduler initialization.
- Implemented `SchedulerFinishEnvelope` and `SchedulerEnvelopeTaskApi` for Quartz job scheduling.
- Created `TempFiles` for service-level temp file management.
- Configured `NLog` for file and console logging.
- Updated `appsettings.json` for connection strings and service-specific configuration.
- Replaced legacy `ProjectInstaller` with `AddWindowsService()` for SCM integration.

EnvelopeGenerator.Service/TempFiles.cs

@@ -0,0 +1,75 @@
+namespace EnvelopeGenerator.Service;
+
+/// <summary>
+/// Service-level temp file management. Mirrors <c>TempFiles.vb</c> from the legacy project.
+/// Manages <c>%TEMP%\EnvelopeGenerator</c> at host startup and shutdown.
+/// 
+/// NOTE: This is independent from <c>EnvelopeGenerator.CommonServices.TempFiles</c>, which is
+/// instantiated inside each Quartz job via <see cref="DigitalData.Modules.Logging.LogConfig"/>.
+/// Do not confuse the two.
+/// </summary>
+public sealed class TempFiles
+{
+    private readonly ILogger<TempFiles> _logger;
+
+    public string TempPath { get; }
+
+    public TempFiles(ILogger<TempFiles> logger)
+    {
+        _logger = logger;
+        TempPath = Path.Combine(Path.GetTempPath(), "EnvelopeGenerator");
+    }
+
+    public bool Create()
+    {
+        try
+        {
+            if (!Directory.Exists(TempPath))
+            {
+                Directory.CreateDirectory(TempPath);
+            }
+            else
+            {
+                CleanUpFiles();
+            }
+
+            return true;
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to create temp directory: {TempPath}", TempPath);
+            return false;
+        }
+    }
+
+    private void CleanUpFiles()
+    {
+        try
+        {
+            foreach (var file in Directory.GetFiles(TempPath))
+            {
+                _logger.LogDebug("Deleting temp file: {File}", file);
+                File.Delete(file);
+            }
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to clean up temp files in: {TempPath}", TempPath);
+        }
+    }
+
+    public bool CleanUp()
+    {
+        try
+        {
+            _logger.LogDebug("Deleting temp directory: {TempPath}", TempPath);
+            Directory.Delete(TempPath, recursive: true);
+            return true;
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Failed to delete temp directory: {TempPath}", TempPath);
+            return false;
+        }
+    }
+}