feat(configmanager): add IFileSystem abstraction

Add file system abstraction to enable testability for file operations.
- IFileSystem interface with common file operations
- FileSystem implementation wrapping System.IO
- Unit tests for FileExists functionality

NEW/src/Utils/JdeScoping.ConfigManager/Services/FileSystem.cs

@@ -0,0 +1,40 @@
+namespace JdeScoping.ConfigManager.Services;
+
+/// <summary>
+/// Real file system implementation.
+/// </summary>
+public class FileSystem : IFileSystem
+{
+    public bool FileExists(string path) => File.Exists(path);
+
+    public bool DirectoryExists(string path) => Directory.Exists(path);
+
+    public async Task<string> ReadAllTextAsync(string path, CancellationToken ct = default)
+        => await File.ReadAllTextAsync(path, ct);
+
+    public async Task WriteAllTextAsync(string path, string content, CancellationToken ct = default)
+        => await File.WriteAllTextAsync(path, content, ct);
+
+    public Task<string[]> GetFilesAsync(string directory, string pattern, CancellationToken ct = default)
+        => Task.FromResult(Directory.GetFiles(directory, pattern));
+
+    public async Task CopyFileAsync(string source, string destination, CancellationToken ct = default)
+    {
+        var content = await File.ReadAllBytesAsync(source, ct);
+        await File.WriteAllBytesAsync(destination, content, ct);
+    }
+
+    public Task DeleteFileAsync(string path, CancellationToken ct = default)
+    {
+        File.Delete(path);
+        return Task.CompletedTask;
+    }
+
+    public string GetDirectoryName(string path) => Path.GetDirectoryName(path) ?? string.Empty;
+
+    public string GetFileName(string path) => Path.GetFileName(path);
+
+    public string GetFileNameWithoutExtension(string path) => Path.GetFileNameWithoutExtension(path);
+
+    public string Combine(params string[] paths) => Path.Combine(paths);
+}

NEW/src/Utils/JdeScoping.ConfigManager/Services/IFileSystem.cs

@@ -0,0 +1,19 @@
+namespace JdeScoping.ConfigManager.Services;
+
+/// <summary>
+/// Abstraction for file system operations to enable testing.
+/// </summary>
+public interface IFileSystem
+{
+    bool FileExists(string path);
+    bool DirectoryExists(string path);
+    Task<string> ReadAllTextAsync(string path, CancellationToken ct = default);
+    Task WriteAllTextAsync(string path, string content, CancellationToken ct = default);
+    Task<string[]> GetFilesAsync(string directory, string pattern, CancellationToken ct = default);
+    Task CopyFileAsync(string source, string destination, CancellationToken ct = default);
+    Task DeleteFileAsync(string path, CancellationToken ct = default);
+    string GetDirectoryName(string path);
+    string GetFileName(string path);
+    string GetFileNameWithoutExtension(string path);
+    string Combine(params string[] paths);
+}