Fixed alpha channel not being respected in colors during HTMLExport

[adrianlanzi]

Fix: Include alpha channel in color representation for HTMLExport

Description:

• Modified the HTMLColorCode function in the ExportUtils class to include the alpha channel in color representation for HTMLExport in FastReport.
• The previous implementation using ColorTranslator.ToHtml() did not account for the alpha channel, resulting in incorrect color representation in exported HTML.
• The modified function now properly handles the alpha channel, ensuring accurate color representation in the exported HTML.
• Tested the modification locally and verified its effectiveness.

#667