Replace turbo confirmation dialogs with custom delete modals

[jstarner]

Description

This PR improves the deletion UX for cards and boards by replacing the browser-native turbo_confirm dialogs with custom, styled modals.

Changes

• Card Deletion: Added app/views/cards/_delete.html.erb to implement custom delete confirmation modal.
• Board Deletion: Updated app/views/boards/edit/_delete.html.erb to use the same accessible modal pattern.
• Cleanup: Removed the now unused button_to_delete_card helper method from app/helpers/cards_helper.rb.

Before

After

[andyra]

Lovely work, @jstarner! I'd suggest centering the buttons, but this looks great otherwise. Thanks for taking initiative.

[jstarner]

Lovely work, @jstarner! I'd suggest centering the buttons, but this looks great otherwise. Thanks for taking initiative.

Thank you @andyra and appreciate the feedback! Love the work y'all are doing and happy to be able to contribute. I've updated the buttons to be centered and included updated screenshots 🙌