Implement About Page and Dark/Light Theme

Description

Implement a new About page for the Web Live Dictation app and add complete dark/light theme support across the application.

About Page Requirements

• Add application overview
• Show key features and ASR capabilities
• Include Gonthuka/WebGPU/WASM information
• Add responsive and clean UI
• Add navigation route to About page

Theme Requirements

• Implement dark/light mode toggle
• Persist selected theme across reloads
• Update all components for theme compatibility
• Ensure proper colors, contrast, and accessibility
• Add smooth theme switching experience

Acceptance Criteria

• About page is accessible and responsive
• Theme toggle works globally
• Theme persists after refresh
• UI works correctly in both dark and light modes
• No broken styles or inconsistent components