Add CI/CD pipeline with security scanning

Description

This MR adds a comprehensive CI/CD pipeline with automated security scanning to the web-dashboard project.

Changes

• ✅ Added .gitlab-ci.yml with build, test, and security stages
• ✅ Enabled Dependency Scanning for npm packages
• ✅ Enabled SAST (Static Application Security Testing) using Semgrep
• ✅ Enabled Secret Detection to catch accidentally committed secrets
• ✅ Configured caching for node_modules to speed up pipeline
• ✅ Added artifact retention for build outputs

Pipeline Stages

1. Build: Compiles the React TypeScript application
2. Test: Runs unit tests with coverage reporting
3. Security: Runs dependency scanning, SAST, and secret detection

Expected Security Findings

This pipeline will detect the vulnerable dependencies currently in package.json:

• lodash 4.17.15 (CVE-2020-8203)
• minimist 1.2.5 (CVE-2020-7598, CVE-2021-44906)
• axios 0.21.1 (CVE-2023-45857)

These will be addressed in a follow-up MR.

Testing

• Pipeline should trigger automatically on this MR
• Build and test stages should pass
• Security scans should detect known vulnerabilities

Closes #13

cc @sabrina @bill