fix: add background task to onboarding order sync + migrate to GitLab

Onboarding fixes:
- Add missing background task trigger for order sync (step 4)
- Import process_historical_import task in onboarding API

GitLab migration:
- Update audit rules to support both GitHub and GitLab paths
- Add .gitlab-ci.yml with lint, test, security, build stages
- Add merge request template (.gitlab/merge_request_templates/default.md)
- Update validate_audit.py to check for GitLab equivalents

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.audit-rules/change_management.yaml

@@ -55,6 +55,7 @@ rules:
       type: file_exists
       paths:
         - ".github/PULL_REQUEST_TEMPLATE.md"
+        - ".gitlab/merge_request_templates/*.md"
       message: "Pull request template recommended"
 
   - id: CHANGE-REV-002
@@ -73,6 +74,7 @@ rules:
       type: file_exists
       paths:
         - ".github/CODEOWNERS"
+        - "CODEOWNERS"  # GitLab uses root CODEOWNERS or .gitlab/CODEOWNERS
         - "CODEOWNERS"
       message: "Consider defining code owners for critical paths"
 
@@ -89,6 +91,7 @@ rules:
       paths:
         - ".github/workflows/ci.yml"
         - ".github/workflows/test.yml"
+        - ".gitlab-ci.yml"
       message: "CI workflow for automated testing required"
 
   - id: CHANGE-CI-002
@@ -99,6 +102,7 @@ rules:
       type: pattern_recommended
       paths:
         - ".github/workflows/*.yml"
+        - ".gitlab-ci.yml"
       patterns:
         - "security|bandit|safety|snyk|trivy"
       message: "Consider security scanning in CI pipeline"
@@ -111,6 +115,7 @@ rules:
       type: pattern_required
       paths:
         - ".github/workflows/*.yml"
+        - ".gitlab-ci.yml"
       patterns:
         - "ruff|flake8|pylint|mypy|lint"
       message: "Code quality checks required in CI"
@@ -141,6 +146,7 @@ rules:
       paths:
         - ".github/workflows/release.yml"
         - ".github/workflows/deploy.yml"
+        - ".gitlab-ci.yml"
         - "Dockerfile"
       message: "Automated deployment process recommended"
 
@@ -193,6 +199,7 @@ rules:
       paths:
         - "Dockerfile"
         - ".github/workflows/*.yml"
+        - ".gitlab-ci.yml"
       patterns:
         - "tag|version|:v"
       message: "Container image versioning recommended"