Improve UI: Move bundle size tab first, remove file types, implement enhanced navigation design

[Copilot]

This PR implements the requested UI improvements to enhance the dashboard's user experience and focus on the most important metrics.

Changes Made

Tab Reordering and Cleanup

• Bundle Size tab is now first and selected by default instead of Build Time
• File Types tab completely removed - dashboard now focuses on the two core metrics: Bundle Size and Build Time
• Cleaned up unused file types data processing code and chart rendering logic
• Updated statistics cards - replaced "Total File Types" with "Bundle Size Range" showing size variation across versions

Enhanced Navigation Design

• Transparent navigation container background for cleaner visual hierarchy that doesn't compete with main content
• Rich button interactions with enhanced visual feedback including borders, shadows, and smooth transforms
• Sophisticated hover and active states with animated gradients and depth effects
• Smooth transitions (0.3s) for premium feel and better user experience
• Better accessibility with improved focus states and touch targets

Technical Improvements

• Simplified chart rendering logic by removing complex conditional branches for file types
• Reduced bundle size by eliminating unused code paths
• Maintained backward compatibility for existing data structures
• All linting and build tests pass

Before and After

Before: 3 tabs (Build Time, Bundle Size, File Types) with Build Time selected by default and basic navigation styling
After: 2 tabs (Bundle Size, Build Time) with Bundle Size selected by default and enhanced interactive navigation with transparent background

The dashboard now provides optimal visual balance with a clean transparent navigation area and rich interactive feedback that guides users naturally toward the most important bundle size metrics.

Fixes #40.

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[Boshen]

@copilot remove the background from the tabs

[Copilot]

@copilot remove the background from the tabs

Background removed from tabs (commit b4235ca). The tabs now use transparent backgrounds with border-based visual feedback for a cleaner appearance.

[Boshen]

@copilot remove the transparent backgrounds with border-based visual feedback from the tabs.

[Copilot]

@copilot remove the transparent backgrounds with border-based visual feedback from the tabs.

Removed all border-based visual feedback from tabs (commit 04d1777). The tabs now use a minimal text-only design with no borders, shadows, or background effects.

[Boshen]

@copilot revert the previous change.

I meant remove the background from dashboard-nav, not the buttons.

[Copilot]

@copilot revert the previous change.

I meant remove the background from dashboard-nav, not the buttons.

Reverted the previous change and removed background from the .dashboard-nav container instead of the buttons (commit c4e62c5). The navigation now has a transparent background while maintaining enhanced button visual feedback with borders, shadows, and animations.