Math SVG Generator API - Cloudflare Workers + @hono/zod-openapi

Endpoints:
- POST /api/svg/generate - Generate SVG from math text
- POST /api/svg/get - Get cached SVG or generate new one
- POST /api/shape/generate - Generate geometric shapes as SVG
- GET /sandbox - Test sandbox page (math tab default)
- GET /sandbox/math - Test sandbox page (math tab)
- GET /sandbox/shape - Test sandbox page (shape tab)
- GET /api/openapi.json - OpenAPI specification
- GET /api/docs - Interactive API documentation UI