Release v0.2.11 — open-redirect hardening + docs cleanup

Security:
- Response::redirect() rejects leading/trailing whitespace and backslash.
  Closes a real open-redirect / stored-XSS bypass of v0.2.5's scheme guard:
  '   javascript:alert(1)' was getting through because the regex anchor
  failed to match URLs with leading whitespace, and browsers strip the
  whitespace before parsing the Location header.
- All v0.2.5 through v0.2.10 are affected. Upgrade recommended for any
  app that passes user input directly to Response::redirect().
- 7 new redirect regression tests.

Tests:
- 17 new RequestContext invariants tests pinning the v0.2.6 architectural
  contracts (class_alias identity, strict __set, response state location,
  ApacheContext lazy alloc, etc.).

Docs:
- deployment.php env var table rewritten with all 20 ZEALPHP_* vars.
- migration / sessions / middleware / README updated for v0.2.6+ rename
  and v0.2.10 additions.

193 unit tests, PHPStan green. See CHANGELOG.md and CRITIC.md.