script-src 'self' 'unsafe-inline' added to admin Content-Security-Policy.
default-src 'self' was blocking OverType editor init block and
the dev live-reload poller. Admin section is auth-gated so
unsafe-inline is acceptable.
Silence mkdir() with @ operator; guard file_put_contents with
is_writable() check. When storage/cache/rate_limit is not writable
by php-fpm, requests are allowed through instead of throwing
warnings that flood the nginx error log.