Feature Implementation: Animated Progress, Themes, and Custom Backgrounds

This issue outlines the features implemented in Pull Request #351, introducing major visual improvements and customization options to the stopwatch.

✨ Core Features
🌀 Animated Progress Circle / Bars

Added a circular progress indicator around the main timer display.

Implemented animated progress bars for each lap, scaled relative to their duration.

Visually demonstrates elapsed time by filling and smoothly resetting every minute.

🎨 Theme Packs / Seasonal Themes

Introduced new seasonal theme packs for user customization.

The selected theme persists across sessions using local storage.

🖼️ Custom Backgrounds / Video Upload

Users can now set custom images or videos as stopwatch backgrounds.

Includes error handling for file selection and video upload.

✅ Implementation Status

💻 Fully responsive UI while maintaining existing core functionality.

⌨️ Keyboard shortcuts remain functional.

🧩 Adds new features only; no existing functionality affected.

🧪 Tested and verified for smooth performance.

🎉 Hacktoberfest 2025 Ready!

This contribution follows Hacktoberfest best practices ✅

Made with ❤️ by [Jwel Srivastava](https://github.com/JwelSrivastava)