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/Commands/ValidateCommandTests.cs

@@ -31,6 +31,7 @@ public class ValidateCommandTests
         services.AddSingleton(_autoDiscoveryService);
         services.AddSingleton(_validationService);
         services.AddSingleton(_runtimeValidationService);
+        services.AddTestLogging();
         _serviceProvider = services.BuildServiceProvider();
 
         _configPathOption = new Option<string?>(["--config-path", "-c"]);
@@ -193,10 +194,10 @@ public class ValidateCommandTests
             rootCommand.AddGlobalOption(_verboseOption);
             rootCommand.AddGlobalOption(_quietOption);
 
-            // Capture console error output
-            var originalErr = Console.Error;
+            // Capture console output (Serilog writes all output to stdout)
+            var originalOut = Console.Out;
             using var writer = new StringWriter();
-            Console.SetError(writer);
+            Console.SetOut(writer);
 
             try
             {
@@ -205,11 +206,11 @@ public class ValidateCommandTests
 
                 // Assert
                 var output = writer.ToString();
-                output.ShouldContain("Error");
+                output.ShouldContain("Connection string 'LocalCache' is required");
             }
             finally
             {
-                Console.SetError(originalErr);
+                Console.SetOut(originalOut);
             }
         }
         finally