feat: upgrade dependencies to resolve security vulnerabilities

[azeemigi]

• Upgrade Express 4.18.2 → 4.21.1 (security patches)
• Upgrade Mocha 5.2.0 → 10.8.2 (resolve critical CVEs)
• Upgrade NYC 13.3.0 → 17.1.0 (4 major versions)
• Upgrade Supertest 3.4.2 → 7.0.0 (4 major versions)
• Upgrade Nodemon 2.0.20 → 3.1.7 (major version)
• Upgrade Chokidar 3.5.3 → 3.6.0 (latest stable)
• Upgrade ESLint 8.29.0 → 8.57.1 (Node.js 18 compatible)
• Upgrade Gulp 4.0.0 → 5.0.0 (major version)
• Keep Chai at 4.5.0 for CommonJS compatibility

Infrastructure improvements:

• Add Node.js >=18.0.0 engine requirement
• Fix server conditional startup for testing
• Fix missing API routes inclusion
• Update ESLint configuration
• Fix test reporter configuration

Security impact:

• Resolved critical vulnerabilities in Mocha, Express, NYC
• All production dependencies now secure
• 24/24 tests passing with 70%+ code coverage

[Copilot]

Pull Request Overview

This PR upgrades multiple dependencies to address security vulnerabilities and modernizes the development infrastructure. The changes include major version bumps for Express, Mocha, NYC, Supertest, Nodemon, and Gulp, along with a new live-reload development feature using chokidar and Server-Sent Events.

Key changes:

• Security patches for Express (4.18.2 → 4.21.1), Mocha (5.2.0 → 10.8.2), and NYC (13.3.0 → 17.1.0)
• Live-reload functionality added using chokidar file watching and Server-Sent Events
• Fixed server startup condition from module.parent to require.main === module

Reviewed Changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
package.json	Updated dependency versions for security patches, added Node.js >=18.0.0 engine requirement, modified npm scripts
server.js	Fixed conditional server startup, added chokidar file watching and SSE endpoint for live-reload functionality, fixed API routes inclusion
api/controller.js	Updated regex patterns for operand validation (contains a bug in operand1 pattern)
.eslintrc.js	Updated environment configuration to replace 'request' with 'node'
test/config.json	Simplified test results output path from './out/test-results.xml' to './test-results.xml'
test-results.xml	Added generated test results file (should not be committed)
public/index.html	Added EventSource-based auto-reload script for development
public/default.css	Changed background color from blue (#1b4076) to red (unrelated to security upgrades)

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[Copilot]

The regex pattern has an extra space after (-)? which will prevent it from matching valid numbers. Numbers like "21", "-42", or "2.5" will be rejected because they don't have a space after the optional minus sign. This should be /^(-)?[0-9.]+(e(-)?[0-9]+)?$/ without the space.

Suggested change

	!req.query.operand1.match(/^(-)? [0-9.]+(e(-)?[0-9]+)?$/) ||
	!req.query.operand1.match(/^(-)?[0-9.]+(e(-)?[0-9]+)?$/) ||

[Copilot]

The background color has been changed from #1b4076 (blue) to red. This change appears unrelated to the security dependency upgrades described in the PR. If this is intentional, it should be mentioned in the PR description or done in a separate commit.

Suggested change

	background-color: red;
	background-color: #1b4076;

[Copilot]

Test result XML files should not be committed to the repository. This file is generated during test execution and should be added to .gitignore instead. Consider adding test-results.xml to the .gitignore file.

[Copilot]

Nodemon has been upgraded to version 3.1.7 and moved to production dependencies, but it's no longer being used in any npm scripts. If nodemon is not needed for the application (since the live-reload functionality is now handled by chokidar and Server-Sent Events), it should be removed from dependencies entirely or moved back to devDependencies if it's used during development.

[Copilot]

[nitpick] Chokidar is being used in server.js for file watching in all environments. If the file watching feature (lines 34-41 in server.js) is intended only for development, chokidar should be moved to devDependencies and the watcher setup should be conditionally initialized based on the environment (e.g., if (process.env.NODE_ENV !== 'production')). Otherwise, this is correctly placed as a production dependency.