feat(namespace): update namespace declarations in source files

[CalvinAllen]

Summary

Add functionality to update namespace declarations in all .cs files within the project when renaming.

Changes Made

• New: Services/SourceFileService.cs - Utility class for source file namespace updates
  • UpdateNamespacesInProject() - Scans all .cs files in project directory
  • UpdateNamespacesInFile() - Updates namespaces in a single file
  • Handles block-scoped namespaces: namespace OldName { }
  • Handles file-scoped namespaces: namespace OldName;
  • Handles nested namespaces: namespace OldName.SubNamespace
  • Preserves file encoding (detects BOM for UTF-8, UTF-16, UTF-32)
• Modified: RenamifyProjectCommand.cs - Calls SourceFileService after updating project file
• Modified: .csproj - Added new file reference

Test Plan

• Build and debug the extension
• Create a test project with various namespace styles:
  • Block-scoped: namespace MyProject { }
  • File-scoped: namespace MyProject;
  • Nested: namespace MyProject.Models { }
• Rename the project
• Verify all namespace declarations are updated
• Verify nested namespaces preserve their suffix (e.g., NewName.Models)
• Verify file encoding is preserved

Closes #8