docs(agents): add Cursor Cloud dev environment setup notes

[drozhzhin-n-e]

Summary

• Documents the Cursor Cloud dev environment under AGENTS.md → ## Cursor Cloud specific instructions so future agents can run both apps without re-discovering setup.
• Captures non-obvious web-stack gotchas found while setting up: the committed apps/web/src/index.html CSP blocks the browser app from reaching local Supabase (pre-existing, same cause as the failing web-e2e CI job on main), email confirmation being enabled, and service-worker caching on localhost.
• No application code or config changed.

Checklist

• npx nx run-many -t lint runs (pre-existing code errors on main, unchanged by this PR)
• npx nx run-many -t test --projects=ports passes
• npx nx build web succeeds
• Changes follow architecture rules (docs-only change)
• New UI uses @spartan-ng/helm/* primitives and signal APIs (n/a — docs only)
• No hardcoded strings — Transloco keys for user-facing text (n/a — docs only)

Test plan

Set up the full dev environment and verified each surface:

• Demo app (npx nx serve demo, :4200) — signed in and created an API key end-to-end in the browser.
  demo_app_create_api_key.mp4
  Demo API key created

• Web full-stack — installed Docker (fuse-overlayfs), started local Supabase (npm run db:start + db:reset), built (npx nx build web) and ran (npm run start:web, :4201). The browser UI is blocked by the committed CSP (documented), so the backend flow was verified via the same Auth/RPC path the app uses: signup → email-OTP confirm (Mailpit) → create_organization RPC, persisting an org with the user as owner.
  web_backend_e2e_verification.log

• ✅ npx nx run-many -t test --projects=ports

• ✅ npx nx build demo / npx nx build web

• ⚠️ npx nx run-many -t lint --all (runs; pre-existing lint errors on main, not introduced here)

Related issues

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