docs: Phase 0 risk assessment for Universal App Builder

- Comprehensive technical feasibility study
- Legal compliance analysis (Dutch KvK, GDPR, API ToS)
- Resource requirements and budget estimation
- Ethical AI usage guidelines (no free API scraping)
- 6-phase implementation roadmap with timelines
- Risk mitigation strategies for self-modification
- Competitive analysis and market positioning
- Revenue projections and break-even analysis

Status: Awaiting stakeholder approval before Phase 1
Branch: feature/universal-app-builder (isolated from main)

Author: CalorieApp Maintainer