chore: Complete ESLint 10 upgrade with breaking changes

[coderabbitai]

Overview

This issue tracks the complete implementation of the ESLint 10 upgrade, which requires several coordinated breaking changes.

Background

PR #341 started the ESLint upgrade but is incomplete. ESLint 8→9 and 9→10 are breaking changes that require:

• typescript-eslint package upgrades
• Configuration migration to flat config format
• Node.js version bump
• CI workflow updates

Required Changes

• Upgrade @typescript-eslint/eslint-plugin and @typescript-eslint/parser to at least v8.56.0 (first version with ESLint 10 support)
• Migrate from .eslintrc.js to eslint.config.mjs (flat config format)
• Remove .eslintignore and integrate ignore patterns into flat config
• Update engines.node in package.json to >=20.19.0 (ESLint 10 requirement)
• Update GitHub workflows to remove Node.js 16.x and 18.x (no longer supported)

Reference Implementations

• Config migration: chore(deps:js): bump deps language#536
• Node.js version bump: chore(js): make node@20.19.0 the minimum supported version language#535
• Migration guide: https://eslint.org/docs/latest/use/migrate-to-10.0.0

Context

• Related PR: chore: npm audit fix #341
• Discussion: chore: npm audit fix #341 (comment)
• Requested by: @rhamzeh

[kcbiradar]

Hi @rhamzeh , can I work on this issue?

[rhamzeh]

@kcbiradar - absolutely, we'd love your contribution!

Main guide:

• https://eslint.org/docs/latest/use/migrate-to-10.0.0

The main blockers for the eslint@10 upgrade were:

• eslint@8 => eslint@9 migration, completed in chore(deps): upgrade dependencies #248
• min supported node must be >=20.19.0, completed in chore(deps): upgrade dependencies #248
• typescript-eslint support for eslint@10, added as of v8.56.0

Will assign this to you - if you later decide you can't complete it - no worries, just let us know. We'll un-assign it so someone else can take it