feat: enterprise 6.6.8, begins decoupling retirement view

[iloveagent57]

Includes logic to send signal with args now required by enterprise signal handlers in: openedx/edx-enterprise#2559

Deployments of new edx-enterprise releases, including:
https://github.com/edx/edx-platform/pull/175/changes

are blocked until this PR is merged. They are blocked because CI fails on pytest openedx/core/djangoapps/user_api/accounts/tests/test_retirement_views.py due to a signal expecting required args that are not present without this fix.

[Copilot]

Pull request overview

This PR unblocks upgrading edx-enterprise by updating the LMS retirement signal emission to include newly-required kwargs expected by enterprise signal handlers, and bumps the pinned edx-enterprise dependency to 6.6.8.

Changes:

• Bump edx-enterprise from 6.6.7 to 6.6.8 across constraints and edx requirements files.
• Update USER_RETIRE_LMS_CRITICAL.send(...) to include retired_email and retired_username.
• Add Claude-related entries to .gitignore (currently duplicated with existing entries).

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
requirements/edx/testing.txt	Pins edx-enterprise==6.6.8 for test environment consistency.
requirements/edx/doc.txt	Pins edx-enterprise==6.6.8 for docs environment consistency.
requirements/edx/development.txt	Pins edx-enterprise==6.6.8 for dev environment consistency.
requirements/edx/base.txt	Pins edx-enterprise==6.6.8 for base environment consistency.
requirements/constraints.txt	Updates the central constraint to edx-enterprise==6.6.8.
openedx/core/djangoapps/user_api/accounts/views.py	Sends required retirement kwargs on USER_RETIRE_LMS_CRITICAL to satisfy enterprise handlers.
.gitignore	Adds Claude ignore entries (but duplicates existing ones earlier in the file).

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