[TASK] Remove legacy release workflows after replacement validation

Description

Clean up and remove deprecated legacy release workflows after the new modular workflows (cicd_6-release.yml, cicd_7-release-java-variant.yml, cicd_8-manual-deploy.yml) have been fully tested and validated in production.

This is a follow-up to #34637 which introduced the replacement workflows with parallel Java variant build support and manual deployment capabilities.

Current State

Deprecated workflows with usage data:

• legacy-release_maven-release-process.yml - Last used Jan 30, 2026 (replaced by cicd_6-release.yml)
• legacy-release_publish-dotcms-docker-image.yml - Used TODAY Feb 16, 2026 (replaced by cicd_8-manual-deploy.yml)
• legacy-release_comp_maven-build-docker-image.yml - Internal component (dependency of other legacy workflows)

Unused workflows safe for immediate deletion:

• legacy-release_release-trigger.yml - Last used May 26, 2025 (9 months ago)
• legacy-release_publish-docker-image-on-release.yml - Never used
• legacy-release_release-candidate.yml - Never used

Acceptance Criteria

Phase 1: Immediate Cleanup (Week 1)

• Delete legacy-release_release-trigger.yml (9 months unused)
• Delete legacy-release_publish-docker-image-on-release.yml (never used)
• Delete legacy-release_release-candidate.yml (never used)
• Verify no external systems depend on these workflows

Phase 2: Validate New Manual Deploy (2 weeks)

• Team uses cicd_8-manual-deploy.yml for feature branch testing
• Verify safety checks work correctly (version pattern detection)
• Validate artifact namespace separation (Maven suffix)
• Confirm GitHub deployment environment grouping works as expected
• No critical issues reported

Phase 3: Deprecate Manual Deploy Legacy (After validation)

• Delete legacy-release_publish-dotcms-docker-image.yml
• Update team documentation with new workflow usage

Phase 4: Validate New Release Process (After 2+ production releases)

• Confirm cicd_6-release.yml works for standard releases
• Verify cicd_7-release-java-variant.yml works for parallel Java builds
• Monitor for any issues or gaps in functionality

Phase 5: Final Cleanup (After validation complete)

• Delete legacy-release_maven-release-process.yml
• Delete legacy-release_comp_maven-build-docker-image.yml
• Remove deprecation notices from remaining workflows
• Update release documentation

Priority

Medium

Additional Context

Related Issues:

• #34637 - Added parallel Java variant builds and manual deploy workflow

Migration Resources:

• Deprecation notices added to all legacy workflows
• New workflows use modular CI/CD phases for consistency
• Safety checks prevent artifact collision in manual deployments

Timeline Estimates:

• Phase 1 (immediate): Week of Feb 16, 2026
• Phase 2 (validation): Feb 16 - Mar 1, 2026 (2 weeks)
• Phase 3 (manual deploy cleanup): Mar 1, 2026
• Phase 4 (release validation): After 2+ production releases (Mar-Apr 2026)
• Phase 5 (final cleanup): Apr 2026

Team Communication:

• Notify team about new cicd_8-manual-deploy.yml workflow
• Document differences from legacy workflow (environment vs version inputs)
• Provide migration examples for common use cases

Review the listed legacy workflows alongside cicd_6-release.yml, cicd_7-release-java-variant.yml, and cicd_8-manual-deploy.yml, then check the related issue #34637 and linked pull request #34707. Start with the Phase 1 deletion candidates and verify external dependencies before cleanup; done means validated replacement workflows, updated documentation, and removal of all approved legacy workflows.