[DEPLOY-01] Configure the staging environment

[Krisor1986]

Goal

Publish a stable environment for team and professor testing.

Tasks

• Select and document the hosting platform
• Configure PostgreSQL
• Configure environment variables
• Run database migrations
• Deploy frontend and backend
• Add demo seed data
• Run a staging smoke test

Acceptance criteria

• The team can access a stable shared URL
• Login and core flows work against PostgreSQL
• Deployment steps are reproducible

Dependencies

• [CI-01]
• [TEST-01]