feat: Codatta-to-Humanbased migration landing at app.codatta.io

[zouqone]

Summary

Replace the Navigate to=\"/app\" index redirect with a brand-rename landing screen. Visitors who hit app.codatta.io/ now see the canonical Humanbased Design System hero before the legacy app:

            Codatta is now
            Humanbased.

[ Migrate your account ]   -> https://contributor.humanbased.ai/migrate
[ Humanbased.ai        ]   -> https://contributor.humanbased.ai

The page is implemented as src/views/migration-landing.tsx, lazy-imported into app.routes.tsx and mounted at the existing root index slot. Everything under /app/*, /account/*, /m/referral, the frontier/dataset routes, etc. continues to resolve as before.

Why

• Codatta is being rebranded to Humanbased; users hitting the legacy domain should be told (not silently redirected mid-flight).
• The DS team supplied the exact layout in Humanbased Design System (1)/ui_kits/contributor/codatta.html (40x40 black mark + 64/80 bold headline + 288px column of two pills). This PR ports that page into the live router.

Scope (what does NOT change)

• All /app/* deep links still work. Existing users with bookmarks into Codatta land where they used to.
• No global navigation / layout changes. The landing is a one-screen page with its own styles.
• No dependency changes (the package-lock.json churn from a local npm install was reverted out of this PR).
• No backend or codatta-connect changes.

Cross-domain cookie note

The destination https://contributor.humanbased.ai/migrate sets the hb_migrated=true funnel cookie on its own mount. We deliberately do NOT try to set it from this page: browsers reject Domain=.humanbased.ai cookie writes initiated from app.codatta.io (cross-domain), so attempting it would be silent dead code.

Validation

• Local Vite dev (npx vite on this branch) renders the landing at http://localhost:5175/.
• Cross-checked that the two CTAs use <a href> (not useNavigate) so middle-click / Cmd-click still open in a new tab.
• Existing routes confirmed unaffected: /app and /app/... still mount AppLayout and the prior views.
• TypeScript: the touched file imports only react-router-dom + react types already in use by the project; no new transitive dependencies introduced.

Rollback

Revert the PR -- the original Navigate to=\"/app\" is one line of restoration. No data, schema, or cookie state to clean up.

🤖 Generated with Claude Code

[beingzy]

Code Review by ⚡ Codex

🚫 BLOCK

The new root route can fail on direct visits because it introduces a lazy component without an available Suspense boundary. That breaks the main behavior this patch is adding.

Review comment:

• [P1] Wrap the new lazy root route in Suspense — /private/var/folders/5m/vyw4bn4d1t9bmjlqq3wy11tc0000gn/T/crosscheck-repo-01cBw6/src/router/routes/app.routes.tsx:65-65
  When / is loaded directly, this new index route renders a React.lazy component, but the router tree in src/router.tsx does not provide a Suspense boundary. The previous root route was a synchronous <Navigate>, so this change makes the landing page suspend during initial render and can blank/crash the root entry point unless the route is wrapped in Suspense or imported eagerly.

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Reviewed with OpenAI Codex via Crosscheck