ci: add CI/CD pipeline with lint and deploy stages

[madhyamakist]

Summary

Adds GitHub Actions CI/CD pipeline for web-scraper.

What's included:

• lint job: Python 3.12 + ruff lint check
• deploy job: SSH-based deploy to staging-instance (port 5001), health check
• scripts/deploy.sh: Flask deploy script (venv, pip install, graceful restart)
• CI_CD.md: Documentation for pipeline setup, secrets, and troubleshooting

Triggers:

• Push to main only (single-environment service)

Required secrets:

• GCP_SA_KEY, GCP_PROJECT
• GCP_VM_INSTANCE_NAME, GCP_ZONE