Feature: Add keyboard shortcuts for common actions

[vultuk]

Description

Implement keyboard shortcuts to improve productivity and accessibility for power users.

Proposed Shortcuts

• Ctrl/Cmd + K: Clear terminal
• Ctrl/Cmd + L: Clear screen (alias for clear)
• Ctrl/Cmd + D: Disconnect from current session
• Ctrl/Cmd + N: Create new session
• Ctrl/Cmd + S: Show session list
• Ctrl/Cmd + /: Show keyboard shortcuts help
• Ctrl/Cmd + +/-: Increase/decrease font size
• Ctrl/Cmd + 0: Reset font size to default
• Escape: Cancel current operation/close modals

Implementation Details

• Display available shortcuts in a help modal
• Add visual indicators when shortcuts are pressed
• Ensure shortcuts don't conflict with browser defaults
• Make shortcuts customizable through settings
• Support both Mac and Windows/Linux key combinations

Benefits

• Faster navigation and control
• Better accessibility for keyboard-only users
• Improved productivity for power users
• Standard feature in terminal applications

Technical Considerations

• Use event.preventDefault() to override browser defaults where needed
• Store custom shortcuts in localStorage
• Provide option to disable/enable shortcuts