FRE-4661: Implement ShieldAI PR workflow recommendations

- Add Gitea PR template with code review checklist
- Add CODEOWNERS file for review assignment policy
- Update shieldai-workflow.md with implemented workflow
- Add branch-protection-rules.yaml for gt/master protection

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.gitea/pull_request_templates/default.md

@@ -0,0 +1,34 @@
+## Description
+
+Brief description of the changes in this PR.
+
+## Related Issue
+
+Closes: FRE-XXXX
+
+## Code Review Checklist
+
+- [ ] Security impact assessment
+- [ ] Test coverage verification
+- [ ] Type checking (TypeScript)
+- [ ] Linting compliance
+- [ ] Documentation updates
+- [ ] Breaking changes documented
+- [ ] Backward compatibility verified
+
+## Review Assignment
+
+| Change Type | Required Reviewers |
+|-------------|-------------------|
+| General code | Code Reviewer |
+| Security-critical | Code Reviewer + Security Reviewer |
+| API contracts | Code Reviewer + CTO |
+| Database schema | Code Reviewer + Senior Engineer |
+
+## Testing
+
+Describe how the changes were tested.
+
+## Screenshots / Logs
+
+(If applicable)