Finalize provider-neutral BeatDesign release

[erickkkyt]

Summary

• remove the standalone Pricing page and SaaS pricing copy from BeatDesign
• add Nano Banana 2 and Nano Banana 2 Lite across the workspace catalog, composer contracts, icons, and BeatAPI request mapping
• finalize provider-neutral Terms in English and Chinese
• retain the open-source/local-first boundary and external Provider billing ownership

Verification

• pnpm typecheck
• pnpm test — 320 passed
• pnpm i18n:check
• pnpm build
• security scan — clean
• git diff --check

No credentials or local data are included.