[Feature] REST API for Programmatic CGU Generation

[P4ST4S]

Description:
The application has no API for programmatic access. The Pricing page mentions "API complète" for Enterprise tier, but no API exists.

Context/Rationale:
Enterprise customers need API access to integrate CGU generation into their workflows, apps, or platforms. This is a key differentiator for the Enterprise tier and a significant revenue opportunity. Without an API, you cannot serve B2B customers effectively.

Location: components/Pricing.tsx:40

Implementation Suggestion / To-Do:

1. Design RESTful API with endpoints: POST /api/generate, GET /api/documents
2. Implement API key authentication and management
3. Add API rate limiting per tier (e.g., 100 req/day Pro, unlimited Enterprise)
4. Create comprehensive API documentation (OpenAPI/Swagger)
5. Build API key management UI in user dashboard
6. Add webhook support for async generation
7. Implement API usage analytics and monitoring