refactor(core)!: move the document root to the public directory
Everything reachable over HTTP now lives in public/, the code stays in the
repository root and is no longer served. The layout below public/ mirrors the
old one, so not a single URL changes.
The preparation landed earlier: PUBLIC_PATH switching to ROOT_PATH . 'public'
is what actually moves the application.
- nginx: root points at /app/public in both templates.
- webpack: setPublicPath('public') keeps the mix-manifest keys as /themes/...,
the build output moves under public/.
- a root .htaccess forwards requests into public/ and denies access to the code,
for Apache hosting where the document root cannot be changed.
BREAKING CHANGE: the document root must be pointed at public/. Restart php-fpm
after updating, the realpath cache holds the old paths.