feat(website): dual-path integration — Sign in, /cloud page, honest copy (S5)

[oratis]

Part of PLAN_WEB_SIGNUP_v1.0 — milestone S5. Independent of the S1–S4 stack (website only, based on main); ideally merges after the auth stack so the Sign-in link lands on a login page that has all three providers.

What

The site said "no cloud account, nothing to sign up for" while the cloud edition grew a real account system. This PR lands the dual-path invariant (owner directive): self-hosted local stays the flagship and account-free — said louder — and the cloud is the clearly-labeled optional path. 用户可以选择用自己的机器部署，也可以选择云端；权力始终在用户手中。

• Nav: Cloud item + Sign in → cloud.meetlisa.ai (EN + zh-CN)
• New /cloud + /zh-CN/cloud: honest two-path comparison table (account, where the soul lives, autonomy cadence, what stays on your Mac, deletion, price), "the deal, plainly" section (real deletion / no lock-in / the local edition never demotes), signup CTA
• Home: hero + CTA band grow the cloud option; the sovereign console is scoped to "the local edition — the flagship, forever" with the two-paths principle beneath — the strong local claims stay true instead of being quietly contradicted
• Install: lede scoped to the local edition; cloud pointed to as optional
• Privacy (EN + zh-CN, re-dated 2026-07-24): cloud-accounts era terms — exactly what's stored (email, sub / password hash, per-account home), what's processed (metered tokens; usage ledger holds counts, not content), sub-processors (LLM providers, Resend, Stripe, Apple, Google, Cloudflare), and real deletion semantics (full home wipe, all sessions die, no retention window)

Verified

astro build — 12 pages clean. Browser preview of /cloud and /zh-CN/cloud: nav, hero, comparison table all render correctly.

🤖 Generated with Claude Code

[oratis]

Review — merge-ready ✅

Pure static SSG (no client JS/SSR), so open-redirect / reflected-XSS are structurally impossible. Verified: no secret embedded anywhere (the sk-ant…/token strings that grep hits are placeholder examples in pre-existing docs); the "Sign in" link is a static https://cloud.meetlisa.ai (HTTPS, correct host, no redirect/next param); domain consistent across all pages + astro.config; new /cloud + /zh-CN/cloud exist with valid internal links; no set:html; Base.astro header mechanism untouched (no CSP regression). Good, honest local-vs-cloud framing + a full sub-processor list.

Non-blocking accuracy checks (legal/trust, not code): the "No soft-delete, no retention window" / "wipes instantly" copy vs GCS buckets defaulting to 7-day soft-delete — confirm the backend does hard delete + has bucket soft-delete/versioning off, or soften the wording; the "no training on your data" claim vs the third-party LLM providers' terms; and privacy.astro's meta "collects nothing to our servers" now sits in slight tension with Cloud accounts (body discloses it fully). Also the site has no baseline security headers (pre-existing nginx, not this PR) — worth adding now that it funnels users to an auth entry.