Companion project for "The Spring Security Filter Chain Explained". A real
Spring Boot 4.1.1 servlet application whose scenarios are Spring profiles, plus
a diagnostic controller that prints the live FilterChainProxy, the reflected
FilterOrderRegistration table, and the servlet container's own registrations.
Twelve captured transcripts under docs/output/, nine cross-linked doc chapters,
21 assertions.
Also fixes a broken relative link in method-security/docs/01: the cross-module
reference to context-propagation/README.md needed two levels up, not one.
