Release v0.2.13

Framework
- CorsMiddleware: env-var origins (ZEALPHP_CORS_ORIGINS) + one-time
  warning when defaulting to wildcard '*'. Backward-compatible.
- static_handler_locations default fixed — trailing-slash directory
  entries prevent /js intercepting /json (and similar prefix collisions).

Main repo demo / website
- app.php cleanup: PSR-12, drop hardcoded TZ + backtick git describe,
  fix /json session leak, remove /exittest (calls exit() = worker kill)
  and 9 other junk demo routes.
- Demo middleware moved to examples/ with honest names.

Triggered by public app.php line-by-line review. Full trace in CRITIC.md.