Add CI/CD pipeline with security scanning

Description

We need to set up a proper CI/CD pipeline for the web-dashboard with automated testing and security scanning.

Tasks

• Create .gitlab-ci.yml with build, test, and security stages
• Add dependency scanning
• Add SAST scanning
• Configure pipeline to run on MRs
• Add test coverage reporting

Security Scans to Enable

• Dependency Scanning (npm audit)
• SAST (Static Application Security Testing)
• Secret Detection

cc @jean @sabrina