Rework package details view

[Gabriel Dufresne (GabrielDuf)]

This pull request significantly refactors the PackageDetailsViewModel and its associated view to improve separation of concerns, data binding, and UI flexibility. The main changes include switching from text-based to strongly-typed properties for URLs, cleaning up screenshot navigation logic, and moving rich text construction from the view model into the view. Additional improvements include new events and properties to support a more dynamic and maintainable UI.

UI and View Logic Enhancements

• Moved rich text and inline construction (for labels, links, and details) out of the view model and into the view (PackageDetailsWindow.axaml.cs), supporting more flexible and maintainable UI updates.
• Added event handlers in the view for property changes, screenshot navigation, and the new contribute button, and restructured the initialization to update the UI as soon as data is available.

Screenshot Navigation Simplification

• Removed custom command can-execute logic and manual command state updates for screenshot navigation; replaced with simple index bounds checks in the handlers.
• Removed derived properties for screenshot navigation state and replaced with direct logic in the view.

Label and Display Improvements

• Cleaned up and standardized label properties, removing trailing colons and adding new labels for additional UI elements (e.g., source, download installer, not available).
• Updated dependency bullet and navigation symbols to use Unicode glyphs for improved appearance.

Icon and Resource Loading

• Improved icon loading logic to handle both file and HTTP(S) URIs, added error logging, and updated to use the new GetIconUrlIfAny method.

These changes modernize the package details dialog, making it more robust, maintainable, and ready for future UI improvements.