This change improves the handling of quote components when the referenced post cannot be found in the Glimmer Post Stream.
Previously, quotes marked as "not found" would not display any username information, making them difficult to understand contextually.

Key Changes:

• Added conditional logic to hide quote controls (toggle and navigate buttons) when quotedPostNotFound is true
• Introduced shouldDisplayQuoteControls getter to centralize control visibility logic
• Modified the quote controls template to only render when appropriate
• Updated data attributes to include data-can-navigate-to-post for better semantic meaning
• Ensured the username from quotedUsername is properly displayed even for not-found quotes
• Added comprehensive test coverage for the new behavior

The quote component now gracefully handles missing posts by showing the username while hiding interactive controls that would not function properly.