feat: add GraphQL backend and PostgreSQL setup

[erikbsa]

What changed

• Added the Node.js and TypeScript setup for the GraphQL backend.
• Added PostgreSQL connectivity through DATABASE_URL.
• Added server/package-lock.json and npm instructions for the team and the VM.
• Documented the VM configuration, local testing through an SSH tunnel, and database migrations.

Verification

• The GraphQL health query returned ok.
• databaseStatus returned connected during local testing through an SSH tunnel.

Note

The domain schema and database tables are not included. They should be added once we have agreed on the data model. Automatic deployment to the VM is not set up yet.

Closes #36

[alekskjo]

Ser bra ut! Dette gir oss et ryddig grunnoppsett for GraphQL og PostgreSQL, med tydelig håndtering av miljøvariabler og gode instruksjoner for lokal kjøring og VM-en. Det er helt greit at datamodell, migrasjoner, tester og det faktiske Tapfinder-API-et kommer i senere PR-er.

Installasjon og TypeScript-build passerer lokalt. Godkjent ✅