feat: deploy zero-cost Static Space demo

[Kuanyu458]

Summary

• publish the zero-compute frontend as a Hugging Face Static Space
• add a Cloudflare Worker API with Turnstile, SSRF-safe fetching, Durable Object quotas, Gemini structured output, and signed TTS tickets
• generate an exact one-page PDF and normalize the Podcast to about three minutes in the browser
• add deployment workflows, privacy/security documentation, health checks, and third-party notices

Quota behavior

• each network source gets 5 attempts per UTC day instead of 2
• each network source gets 2 successfully completed Podcasts per day
• the site allows 20 successful report generations per day
• fetch, text-model, TTS, or browser MP3 failures release reserved success capacity
• Podcast success is committed only after the browser validates and encodes the MP3
• the UI shows remaining attempts, Podcast successes, and the Taipei reset time

Live preview

• App: https://kuanyu458-link2news-demo.static.hf.space/index.html
• API health: https://link2news-demo-api.ky0808458.workers.dev/healthz

Verification

• 36 Python tests passed
• existing Node Worker tests passed
• 6 Demo contract tests passed
• TypeScript check, compileall, shell syntax, plist lint, public-tree check, diff check, and npm audit passed
• GitHub Actions matrix previously passed on Python 3.10/3.13, Node 20/22, and macOS smoke
• live browser verified that five attempts replace the old two-request block
• three text-format failures did not consume Podcast success quota
• a 118.4/131.0-second TTS processing failure was canceled and did not consume the remaining success quota
• script length is now calibrated to 1,400-1,500 characters from those live TTS measurements

Remaining live acceptance

The tester IP used all 5 anti-abuse attempts while calibrating Gemini output. The final 1,400-1,500-character MP3 duration check must run after the next UTC reset; the quota was not bypassed or reset.

Rollback

Pause or remove the Static Space and Worker. Existing LINE, D1, R2, Mac runner, 15-minute Podcast, and full report behavior are unchanged.