Add confetti animation to shopping basket button

[Copilot]

Summary

This PR adds a celebratory confetti animation that fires across the entire screen whenever a user adds an item to their shopping basket. The animation is implemented exclusively for the web version of the eShop application.

Implementation Details

The implementation uses the lightweight canvas-confetti library (v1.9.2) loaded via CDN. When a user clicks the "Add to shopping bag" button, a spectacular multi-burst confetti animation is triggered with 200 particles that cascade across the screen with varying spreads, velocities, and decay rates.

Changes Made

1. App.razor - Added script references for the canvas-confetti library and custom confetti handler
2. ItemPage.razor - Injected IJSRuntime and added JavaScript interop call to trigger confetti after successfully adding item to basket
3. confetti.js (new) - Created JavaScript function that orchestrates a 5-burst confetti sequence for maximum visual impact

Key Features

• ✨ Spectacular Effect - Multi-burst animation with 200 particles for a celebratory experience
• 🎯 Reliable Triggering - Fires every time the add-to-basket action succeeds
• 🌐 Web-Only Implementation - Isolated to WebApp; HybridApp remains unchanged
• 🪶 Minimal Footprint - Lightweight library (~11KB minified) loaded from CDN
• 🔧 Clean Integration - Uses standard Blazor JavaScript interop patterns

Testing

• ✅ WebApp builds successfully with no errors or warnings
• ✅ JavaScript syntax validated
• ✅ HybridApp verified to be unaffected by changes
• ✅ Demo page created to visualize the confetti effect

Demo

The screenshot shows the demo page with the "Add to shopping bag" button. When clicked, a vibrant confetti animation fills the entire screen, creating a delightful user experience that celebrates the shopping action.

Fixes #[issue-number]

Original prompt

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This section details on the original issue you should resolve

<issue_title>More confetti</issue_title>
<issue_description>Whenever I put a item into the basket on the website, I want to fire off a huge confetti animation across the entire screen. Make sure to activate the confetti every time, I click the add to basket button and only implement this on the web version of this eShop.</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #83

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