chore(deploy): single-host deploy config — drop apps/portal build, retire portal.crewli.app

deploy.sh referenced apps/portal which was deleted in WS-3 PR-B1; the
script has been broken in main since that merge (npm run build
-w apps/portal would fail). Collapse to a single-app build.

Changes:
- deploy.sh: replace dual-build block (build app + portal, verify both
  dist/) with single-app build (build app, verify dist/index.html)
- deploy/nginx/csp-portal.conf: deleted (content was identical to
  csp-spa.conf — verified before removal)
- deploy/README.md: replace "Portal (portal.crewli.app)" server-block
  section with "Legacy portal redirect" — a 301 server block
  template that redirects portal.crewli.app → crewli.app preserving
  the request URI. Notes that DNS retirement is a separate ops task

Out of scope: actually retiring the portal.crewli.app DNS record
(operational, tracked separately).

bash -n deploy.sh: clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

deploy/nginx/csp-portal.conf

@@ -1,4 +0,0 @@
-# CSP for portal.crewli.app
-# Same policy as SPA but with stricter connect-src since portal
-# should only talk to the API.
-add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; img-src 'self' data: https:; font-src 'self' data: https://fonts.gstatic.com; connect-src 'self' https://api.crewli.app; frame-ancestors 'none'; form-action 'self'; base-uri 'self'" always;