UI/UX Polish: Modern design, compact layout, and real-time toggle feedback

• Redesigned popup with gradient header, animated logo, and modern toggle button
• Added quick stats display (words translated, cache hits) to popup
• Improved all pages with consistent gradient headers and emoji icons
• Made extension more compact (280px width, reduced padding throughout)
• Fixed toggle button to update UI immediately on click (real-time feedback)
• Enhanced help page with FAQ section and more translation examples
• Added smooth animations and hover effects throughout
• Improved CSS with variables system for consistent theming
• Updated navigation links with icons and better visual feedback

Added a keyboard shortcut to toggle on and off Type-Nepali without touching the extension. Keyboard shortcut key: Ctrl+Alt+N

Improve error handling, refactor code, and enhance maintainability

- Added error handling to TRANSLATION_API_CALL to manage fetch errors.
- Ensured observer is initialized before disconnection in content.js.
- Refactored translation logic into a separate function to avoid duplication.
- Changed let to const for non-reassigned variables.
- Converted .then() to await in popup.js for async/await consistency.

code refactoring, fixed minor bug, added new gitignore file