Fix unclickable, unselectable links in Avalonia package details

[Gabriel Dufresne (GabrielDuf)]

This pull request refactors how links and license/download rows are rendered in PackageDetailsWindow.axaml.cs, improving code clarity, consistency, and user interaction. It also enhances error handling when opening URLs. The most important changes are grouped below:

UI Refactoring and Consistency Improvements:

• Refactored the rendering of inline rows with URLs and license/download rows to use helper methods (BuildLinkRow, CreateLinkBlock, BoldLabel) for more consistent layout and code reuse. Now, only the URL part is a link, and labels are always rendered in bold.
• Improved the download row to show a bold, selectable link when available, or a consistent "not available" message when not.

User Interaction Enhancements:

• Updated link activation so that only a clean click (not a drag/select) triggers the link, improving usability for selectable, copyable hyperlinks.

Error Handling and Logging:

• Improved error handling in OpenUrl by logging errors with Logger.Error when a URL fails to open, instead of silently swallowing exceptions.