Replace burger menu with tab-based sidebar design

[fx]

Description

Remove the current burger menu implementation and replace it with a tab-based sidebar that overlays the dashboard content instead of pushing it.

Acceptance Criteria

• Remove burger menu implementation
• Create new tab-based sidebar component
• Sidebar overlays content instead of pushing it
• Add heart icon tab as the primary sidebar control

Technical Notes

• Use Radix UI Theme components
• Ensure touch-friendly tab sizes
• Consider using CSS transforms for overlay behavior

Epic: #72