Refactor ShortYou into Astro single-page frontend with modular GAS backend

[HeiTang]

Summary

• replace the legacy static frontend with an Astro single-page app that separates public resolve mode and authorized create mode
• refactor the Google Apps Script backend into config, controller, repository, service, utility, and entrypoint modules
• add env-aware frontend and GAS push/deploy workflows, runtime config bootstrap, and refreshed bilingual README documentation

What changed

• add Astro/Tailwind frontend structure under src/ with shared layout/components and page scripts for alias resolution, create flow, and UI state
• remove the legacy invite-page-based frontend flow and normalize public assets / static hosting layout
• split the GAS implementation into focused TypeScript modules and stop tracking the old generated Code.js source layout
• add wrapper scripts for frontend env loading and GAS push/deploy automation
• update README.md and README.zh-TW.md to document the single-page architecture, commands, and deployment model

Notes for review

• public lookup remains hash-based so the frontend can stay on static hosting
• authorized create mode is now entered through /#t= on the same page instead of a separate invite page
• there is an unstaged local change in docs/backend-spec.zh-TW.md that is intentionally not included in this PR

Verification

• reviewed the branch diff against main
• confirmed the PR source branch is dev and upstream is origin/dev
• existing local uncommitted docs changes were left untouched to avoid mixing unfinished documentation into this PR

[HeiTang]

@copilot please review this pull request for correctness, regressions, architecture issues, and test/documentation gaps. Focus on the Astro single-page frontend flow, the modularized Google Apps Script backend, and the env-aware deployment changes.

[Copilot]

@copilot please review this pull request for correctness, regressions, architecture issues, and test/documentation gaps. Focus on the Astro single-page frontend flow, the modularized Google Apps Scrip...

Addressed in 2b20f66.

Review + fixes completed:

• Fixed a frontend routing regression: entering /#t=<token> no longer rewrites the URL to /; it now preserves the current path/query so project-path/static-host deployments keep working.
• Fixed Pages deployment gap: workflow now passes required frontend env vars (PUBLIC_API_URL, PUBLIC_TURNSTILE_SITE_KEY) from repo vars/secrets during build.
• Expanded Pages workflow path triggers to include scripts/**, tailwind.config.mjs, and tsconfig.json so relevant build/deploy-impacting changes are not skipped.

Validation run:

• npm run typecheck:gas
• npm run build:gas
• npm run check:gas
• PUBLIC_API_URL=... PUBLIC_TURNSTILE_SITE_KEY=... npm run build:frontend
• CodeQL check: 0 alerts.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• telemetry.astro.build
  • Triggering command: /usr/local/bin/node node /home/REDACTED/work/ShortYou/ShortYou/node_modules/.bin/astro build (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

[HeiTang]

@copilot I verified the latest head locally after 2b20f66: npm run typecheck:gas, npm run build:gas, npm run check:gas, and npm run build:frontend all passed. Please review the current PR head again and report only any remaining correctness, regression, architecture, or deployment blockers.

[Copilot]

@copilot I verified the latest head locally after 2b20f66: npm run typecheck:gas, npm run build:gas, npm run check:gas, and npm run build:frontend all passed. Please review the current PR head...

Reviewed current head (2b20f66) again for blocker-level issues only.

I do not see any remaining correctness, regression, architecture, or deployment blockers at this time.

No additional code changes were needed.