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/compliance.yaml

@@ -122,8 +122,10 @@ rules:
       type: file_exists
       paths:
         - ".github/PULL_REQUEST_TEMPLATE.md"
+        - ".gitlab/merge_request_templates/*.md"
         - "CONTRIBUTING.md"
         - ".github/workflows/*.yml"
+        - ".gitlab-ci.yml"
       message: "Code review process must be documented/enforced"
 
   - id: COMP-POL-002
@@ -134,7 +136,10 @@ rules:
       type: file_exists
       paths:
         - ".github/CODEOWNERS"
+        - "CODEOWNERS"
         - ".github/workflows/*.yml"
+        - ".gitlab-ci.yml"
+        - ".gitlab-ci.yml"
       message: "Document change approval requirements"
 
   - id: COMP-POL-003
@@ -161,6 +166,7 @@ rules:
       type: file_exists
       paths:
         - ".github/workflows/ci.yml"
+        - ".gitlab-ci.yml"
         - "pytest.ini"
         - "pyproject.toml"
       patterns:
@@ -175,6 +181,7 @@ rules:
       type: file_exists
       paths:
         - ".github/workflows/*.yml"
+        - ".gitlab-ci.yml"
       patterns:
         - "deploy|release"
       message: "Deployment process must be automated and logged"