feat(lang): add VB.NET support

[CalvinAllen]

Description

Add support for VB.NET projects and source files.

Current Behavior

The extension currently only handles:

• .cs files for namespace and using statement updates
• .csproj files for project file updates

Proposed Changes

• Update SourceFileService to handle .vb files
• Update namespace patterns for VB.NET syntax (Namespace OldName / End Namespace)
• Update imports patterns (Imports OldName)
• Handle .vbproj files in ProjectFileService

VB.NET Syntax Examples

' Namespace declaration
Namespace OldName
End Namespace

' Imports statement
Imports OldName
Imports OldName.SubNamespace

Priority

Low - enhancement for broader language support