refactor: standardize variable naming and file formatting

- Rename Quantity to quantity in BomItem for consistent naming convention
- Update references in MainModule to use lowercase quantity
- Add newlines at end of files for consistency
- Update vba_metadata.json with new source path and document module

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

VBA/ClassModules/BomExtractor.cls

@@ -481,4 +481,4 @@ Public Function GetErrorSummary() As String
         Next msg
         GetErrorSummary = result
     End If
-End Function
+End Function