Initial project setup: Next.js frontend + .NET 9 backend

- Frontend: Next.js 16 + shadcn/ui + Tailwind CSS 4
- Backend: .NET 9 Web API with Npgsql health check
- Docker Compose for prod and dev environments
- Woodpecker CI pipeline for auto-deploy
- Health check endpoints for E2E testing

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/public/file.svg

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