feat: add map providers and persist zoom

[lawvs]

Summary

• add AMap and Baidu web map providers with explicit WGS-84 coordinate handling
• centralize external map provider definitions, options, and URL generation
• validate persisted plugin settings with Zod 4 and persist map zoom as the single source of truth

Testing

• pnpm test
• pnpm exec tsc -p tsconfig.app.json --noEmit --pretty false
• pnpm lint:check
• pnpm format:check
• pnpm build