refactor(configmanager): convert CLI to structured logging with Serilog

Replace Console.WriteLine calls with ILogger usage across all CLI commands.
Serilog is configured via DI with clean message-only output suitable for
CLI tooling. Log levels map to --quiet (Warning), default (Information),
and --verbose (Debug) flags.

- Add Serilog packages and configure in Program.cs
- Convert all 7 command files to use ILoggerFactory from DI
- Add BeginScope with context properties (Command, ConfigPath, etc.)
- Create logging_style.md documenting patterns and best practices
- Update tests with TestLoggingHelper for Serilog test configuration

NEW/tests/Utils/JdeScoping.ConfigManager.Cli.Tests/TestLoggingHelper.cs

@@ -0,0 +1,27 @@
+using Microsoft.Extensions.DependencyInjection;
+using Serilog;
+using Serilog.Events;
+
+namespace JdeScoping.ConfigManager.Cli.Tests;
+
+/// <summary>
+/// Helper for setting up logging in CLI tests.
+/// </summary>
+public static class TestLoggingHelper
+{
+    /// <summary>
+    /// Adds Serilog logging to a service collection configured to write to Console.
+    /// This allows tests to capture log output via Console.SetOut.
+    /// </summary>
+    public static IServiceCollection AddTestLogging(this IServiceCollection services, LogEventLevel level = LogEventLevel.Information)
+    {
+        var logger = new LoggerConfiguration()
+            .MinimumLevel.Is(level)
+            .WriteTo.Console(outputTemplate: "{Message:lj}{NewLine}{Exception}")
+            .CreateLogger();
+
+        services.AddLogging(builder => builder.AddSerilog(logger, dispose: true));
+
+        return services;
+    }
+}