Add Intercom to EasyCLA Landing Page

[mlehotskylf]

Summary

Add Intercom integration to the EasyCLA Landing Page following the LFX canonical pattern.

Context

The landing page is publicly accessible (public-page app), so Intercom must boot anonymously on page load and upgrade to identified when the user logs in.

Work

• Angular changes: feat: add Intercom integration easycla-landing-page#80
• Auth0 changes (Intercom JWT claim for "LF CLA" + 127.0.0.1 dev origin): linuxfoundation/auth0-terraform#257

Acceptance criteria

• Intercom launcher visible on landing page for anonymous visitors
• Chat bubble shows correct user identity after login
• Session shuts down and re-boots anonymous on logout

[mlehotskylf]

Here is the PR:

• feat: add Intercom integration easycla-landing-page#80
• fix: shutdown Intercom session on logout easycla-landing-page#81