Add keyboard shortcuts for common actions (like, repost)

[aleibovici]

Description

Add keyboard shortcuts for common feed actions to improve power-user experience. For example, pressing L to like a focused post, R to repost, J/K to navigate between posts.

Suggested approach

• Add a keyboard event listener (consider a custom hook like useKeyboardShortcuts)
• Start with basic shortcuts: L (like), R (repost), J (next post), K (previous post)
• Only activate when no text input is focused
• Optionally add a ? shortcut to show a help overlay listing all shortcuts

Files to look at

• src/components/ — feed and post card components
• src/hooks/ — existing custom hooks for patterns to follow

A fun feature that touches event handling and component state.