[USERSTORY] Setup Dev/Test Environment

[simonengstler]

1. As a developer
2. I want to test functionality under realistic conditions on a non-productive system
3. So that I can improve overall product quality

I suggest calling it "dev(elopment) environment", as it's not just for testing.

Acceptance Criteria

• Select and register domain name (e.g. bewerbung.dev.generation-d.org, bewerbung-test.generation-d.org)
• Setup/ double-check test server
• Connect Supabase Test-DB
• Possibly add some anonymized mock data from last year or create something from scratch
• Make sure that it always has the newest version from main