Add Intercom to EasyCLA Corporate Console

[mlehotskylf]

Summary

Add Intercom integration to the EasyCLA Corporate Console following the LFX canonical pattern.

Context

The Corporate Console is an auth-only app — users must log in before seeing content. Intercom should boot only after login (no anonymous boot needed).

Work required

• Create IntercomService in core/services/ (reuse pattern from easycla-landing-page#80)
• Wire identified boot into the root component's auth subscription
• Add intercomId, auth0IntercomClaim, auth0UsernameClaim to environment files
• Add Auth0 custom_claims case for the Corporate Console client name in auth0-terraform

Acceptance criteria

• Chat bubble appears after login with correct user identity
• Session shuts down on logout