feat: migrate to ESLint v9 flat config and update dependencies

[jfrench9]

Summary

This PR migrates the project to ESLint v9's new flat configuration format and updates Next.js along with other dependencies to their latest versions. The changes modernize the development toolchain while maintaining code quality standards.

Key Changes

ESLint Configuration Migration

• ✅ Migrated from legacy .eslintrc.cjs to modern eslint.config.js (flat config)
• ✅ Removed deprecated .eslintignore file (ignore patterns now in main config)
• ✅ Updated ESLint rules and plugin configurations for v9 compatibility

Dependency Updates

• ✅ Updated Next.js to latest version with improved performance and features
• ✅ Updated TypeScript, Vitest, and other development dependencies
• ✅ Refreshed package-lock.json with optimized dependency tree

File Structure Updates

• ✅ Renamed middleware.ts → proxy.ts for better semantic clarity
• ✅ Updated TypeScript configuration for improved type checking
• ✅ Cleaned up unused ESLint disable comment in EntitySelectorDropdown component

Breaking Changes

⚠️ ESLint Configuration: Projects extending this config will need to update their ESLint setup to use the new flat config format.

Testing Notes for Reviewers

• Verify ESLint rules are working correctly: npm run lint
• Confirm TypeScript compilation: npm run type-check
• Test build process: npm run build
• Run test suite: npm test
• Check that the renamed proxy file functions correctly in development

Browser Compatibility

No impact on browser compatibility - these are development toolchain updates only. The application continues to support the same browser versions as before.

Migration Notes

The ESLint flat config provides better performance and more intuitive configuration management. All existing linting rules have been preserved in the new format.

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🤖 Generated with Claude Code

Branch Info:

• Source: chore/update-packages-jan-26
• Target: main
• Type: feature

Co-Authored-By: Claude noreply@anthropic.com