refactor: migrate logging infrastructure from NLog to Serilog

- Replace NLog packages with Serilog.AspNetCore and related dependencies
- Add Serilog.UI with SQLite provider for log visualization
- Implement environment-based logging configuration:
  * Development: Console output with simplified template
  * Production: File-based logging with separate files per level
- Add SQLite sink for persistent log storage and web UI access
- Configure rolling file policies with configurable retention
- Update appsettings.Logging.json to use Serilog configuration format
- Enable Serilog self-diagnostics for troubleshooting

src/ReC.API/Program.cs

@@ -1,27 +1,96 @@
 using Microsoft.AspNetCore.Rewrite;
 using Microsoft.EntityFrameworkCore;
-using NLog;
-using NLog.Web;
 using ReC.API.Middleware;
 using ReC.Application;
 using ReC.Infrastructure;
+using Serilog;
+using Serilog.Ui.Core.Extensions;
+using Serilog.Ui.SqliteDataProvider.Extensions;
+using Serilog.Ui.Web.Extensions;
 using System.Reflection;
 using LogLevel = Microsoft.Extensions.Logging.LogLevel;
 
-var logger = LogManager.Setup().LoadConfigurationFromAppSettings().GetCurrentClassLogger();
-logger.Info("Logging initialized!");
+// Enable Serilog self-diagnostics
+Serilog.Debugging.SelfLog.Enable(msg => Console.WriteLine($"[SERILOG] {msg}"));
+
+// Build temporary configuration to read log directory from appsettings.Logging.json
+var tempConfig = new ConfigurationBuilder()
+    .SetBasePath(Directory.GetCurrentDirectory())
+    .AddJsonFile("appsettings.json", optional: false)
+    .AddJsonFile("appsettings.Logging.json", optional: false)
+    .AddEnvironmentVariables()
+    .Build();
+
+var isDevelopment = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") == "Development";
+
+var logDirectory = tempConfig.GetValue<string>("Serilog:LogDirectory")
+    ?? Path.Combine(AppContext.BaseDirectory, "logs");
+var retainedFileCountLimit = tempConfig.GetValue("Serilog:RetainedFileCountLimit", 30);
+
+Directory.CreateDirectory(logDirectory);
+
+var sqliteDbPath = Path.Combine(logDirectory, "logs.db");
+var logFilePathTemplate = Path.Combine(logDirectory, ".Rec.API-.log");
+
+Console.WriteLine($"[INFO] Log Directory: {logDirectory}");
+
+// Configure Serilog based on environment:
+//   Development : Console + SQLite (+ Web UI)
+//   Production  : File (per-level) + SQLite (+ Web UI)
+var loggerConfig = new LoggerConfiguration()
+    .MinimumLevel.Information()
+    .MinimumLevel.Override("Microsoft.AspNetCore", Serilog.Events.LogEventLevel.Warning)
+    .MinimumLevel.Override("Microsoft.EntityFrameworkCore", Serilog.Events.LogEventLevel.Warning)
+    .Enrich.FromLogContext();
+
+if (isDevelopment)
+{
+    loggerConfig.WriteTo.Console(outputTemplate: "[{Timestamp:HH:mm:ss} {Level:u3}] {Message:lj}{NewLine}{Exception}");
+}
+else
+{
+    loggerConfig
+        .WriteTo.File(
+            Path.Combine(logDirectory, ".Rec.API-Info.log"),
+            rollingInterval: RollingInterval.Day,
+            retainedFileCountLimit: retainedFileCountLimit,
+            restrictedToMinimumLevel: Serilog.Events.LogEventLevel.Information,
+            outputTemplate: "[{Timestamp:yyyy-MM-dd HH:mm:ss} {Level:u3}] {Message:lj}{NewLine}{Exception}")
+        .WriteTo.File(
+            Path.Combine(logDirectory, ".Rec.API-Warning.log"),
+            rollingInterval: RollingInterval.Day,
+            retainedFileCountLimit: retainedFileCountLimit,
+            restrictedToMinimumLevel: Serilog.Events.LogEventLevel.Warning,
+            outputTemplate: "[{Timestamp:yyyy-MM-dd HH:mm:ss} {Level:u3}] {Message:lj}{NewLine}{Exception}")
+        .WriteTo.File(
+            Path.Combine(logDirectory, ".Rec.API-Error.log"),
+            rollingInterval: RollingInterval.Day,
+            retainedFileCountLimit: retainedFileCountLimit,
+            restrictedToMinimumLevel: Serilog.Events.LogEventLevel.Error,
+            outputTemplate: "[{Timestamp:yyyy-MM-dd HH:mm:ss} {Level:u3}] {Message:lj}{NewLine}{Exception}")
+        .WriteTo.File(
+            Path.Combine(logDirectory, ".Rec.API-Critical.log"),
+            rollingInterval: RollingInterval.Day,
+            retainedFileCountLimit: retainedFileCountLimit,
+            restrictedToMinimumLevel: Serilog.Events.LogEventLevel.Fatal,
+            outputTemplate: "[{Timestamp:yyyy-MM-dd HH:mm:ss} {Level:u3}] {Message:lj}{NewLine}{Exception}");
+}
+
+// SQLite sink is always active (used by Serilog Web UI)
+loggerConfig.WriteTo.SQLite(sqliteDbPath, storeTimestampInUtc: true);
+
+Log.Logger = loggerConfig.CreateLogger();
+
+Log.Information("Logging initialized!");
 
 try
 {
+    Log.Information("Starting ReC.API application");
+
     var builder = WebApplication.CreateBuilder(args);
 
-    builder.Logging.SetMinimumLevel(LogLevel.Trace);
-
-    if (!builder.Environment.IsDevelopment())
-    {
-        builder.Logging.ClearProviders();
-        builder.Host.UseNLog();
-    }
+    // Use Serilog for logging
+    builder.Host.UseSerilog();
 
     var config = builder.Configuration;
 
@@ -71,6 +140,16 @@ try
         c.IncludeXmlComments(xmlPath);
     });
 
+    // Serilog Web UI — SQLite provider, same path used by the SQLite sink above
+    builder.Services.AddSerilogUi(logUIOpt =>
+    {
+        logUIOpt.UseSqliteServer(dbOpt =>
+        {
+            dbOpt.WithConnectionString($"Data Source={sqliteDbPath}");
+            dbOpt.WithTable("Logs");
+        });
+    });
+
     var app = builder.Build();
 
     app.UseMiddleware<ExceptionHandlingMiddleware>();
@@ -89,14 +168,21 @@ try
 
     app.UseAuthorization();
 
+    // Serilog Web UI is always active (both Development and Production)
+    app.UseSerilogUi();
+
     app.MapControllers();
 
     app.Run();
 }
 catch (Exception ex)
 {
-    logger.Error(ex, "Stopped program because of exception");
+    Log.Fatal(ex, "Stopped program because of exception");
     throw;
 }
+finally
+{
+    Log.CloseAndFlush();
+}
 
 public partial class Program;

src/ReC.API/ReC.API.csproj

@@ -23,8 +23,13 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="9.0.11" />
     <PackageReference Include="Swashbuckle.AspNetCore" Version="6.6.2" />  
-	<PackageReference Include="NLog" Version="5.2.5" />
-	<PackageReference Include="NLog.Web.AspNetCore" Version="5.3.0" />
+	<PackageReference Include="Serilog.AspNetCore" Version="10.0.0" />
+	<PackageReference Include="Serilog.Settings.Configuration" Version="10.0.1" />
+	<PackageReference Include="Serilog.Sinks.Console" Version="6.1.1" />
+	<PackageReference Include="Serilog.Sinks.File" Version="7.0.0" />
+	<PackageReference Include="Serilog.Sinks.SQLite" Version="7.0.0" />
+	<PackageReference Include="Serilog.UI" Version="3.2.0" />
+	<PackageReference Include="Serilog.UI.SqliteProvider" Version="1.1.0" />
   </ItemGroup>
 
   <ItemGroup>

src/ReC.API/appsettings.Logging.json

@@ -5,55 +5,8 @@
       "Microsoft.AspNetCore": "Warning"
     }
   },
-  "NLog": {
-    "throwConfigExceptions": true,
-    "variables": {
-      "logDirectory": "E:\\LogFiles\\Digital Data\\Rec.API",
-      "logFileNamePrefix": "${shortdate}.Rec.API"
-    },
-    "targets": {
-      "infoLogs": {
-        "type": "File",
-        "fileName": "${logDirectory}\\${logFileNamePrefix}-Info.log",
-        "maxArchiveDays": 30
-      },
-      "warningLogs": {
-        "type": "File",
-        "fileName": "${logDirectory}\\${logFileNamePrefix}-Warning.log",
-        "maxArchiveDays": 30
-      },
-      "errorLogs": {
-        "type": "File",
-        "fileName": "${logDirectory}\\${logFileNamePrefix}-Error.log",
-        "maxArchiveDays": 30
-      },
-      "criticalLogs": {
-        "type": "File",
-        "fileName": "${logDirectory}\\${logFileNamePrefix}-Critical.log",
-        "maxArchiveDays": 30
-      }
-    },
-    "rules": [
-      {
-        "logger": "*",
-        "level": "Info",
-        "writeTo": "infoLogs"
-      },
-      {
-        "logger": "*",
-        "level": "Warn",
-        "writeTo": "warningLogs"
-      },
-      {
-        "logger": "*",
-        "level": "Error",
-        "writeTo": "errorLogs"
-      },
-      {
-        "logger": "*",
-        "level": "Fatal",
-        "writeTo": "criticalLogs"
-      }
-    ]
+  "Serilog": {
+    "LogDirectory": "E:\\LogFiles\\Digital Data\\Rec.API",
+    "RetainedFileCountLimit": 30
   }
 }