POC: Migrate to NPM workspaces

[piotrbogun]

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Proposed changes

Checklist

• I have read the contribution guidelines
• For non-bugfix PRs, I have discussed this change on the forum/slack team.
• I have run npm run test to verify the unit tests pass
• I have added suitable unit tests to cover the new/changed functionality

Test Summary

Test Type	Command/Method	Expected Result	Actual Result
Full Test Suite	npm test	All tests pass	2799 passing, 61 pending, 0 failing
Build Verification	npm run build	Build succeeds	✅ Succeeded
Symlink Verification	ls -la node_modules/@node-red/	Symlinks point to packages/*	✅ Correct symlinks created
Dependency Check	node scripts/verify-package-dependencies.js	Script passes	✅ Passed
JSHint Linting	npx grunt jshint:nodes	Lints core node files	✅ 37 files linted (62 pre-existing errors unrelated to migration)
Watch Test (Flaky)	Ran specific watch test 5 times consecutively	No intermittent failures	✅ All 5 runs passed after fix