Initial scaffold: offertesysteem (clients, projects, quotes, quote_items)

- Next.js 15 + TypeScript + Tailwind, standalone output
- SQLite schema: users, clients, projects, quotes, quote_items
- HMAC-signed sessie-cookie auth
- Dockerfile (Node 22 Alpine, multi-stage)
- create-admin script
- Doel: portal.rikxplatform.nl

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

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