Remove Q.js lib

[grosbouddha]

Drop the q.js promise library in favor of native Promise:

• Q.defer() → new Promise((resolve, reject) => ...)
• Q.resolve / Q.reject → Promise.resolve / Promise.reject
• Q.all([...]) → Promise.all([...])
• Q([]) → Promise.resolve([])

No Q-specific features were used anywhere in app code, so the migration is pure 1:1 with no behavior changes.

The trickiest part was ensuring proper this binding where needed - constructing a Promise requires an anonymous function that shadows the enclosing this.

TESTED=Unit tests and E2E passing

[juliandescottes]

Thanks! Now that looks like JS from 2017 or something :)

[juliandescottes]

Just checking if this is intentional.

Follow up: Noticed we are only linting on src/
We should extend to tests/ no reason not to lint and format test code.