The cookie SecurePolicy was hard-coded to Always, so the auth cookie was always
marked Secure and the browser never sent it over plain HTTP — making login
impossible on the HTTP-only Docker dev cluster (login succeeded server-side but
every following request was unauthenticated). Add SecurityOptions.RequireHttps-
Cookie (default true — production stays HTTPS-only); when false the cookie uses
SameAsRequest. The docker/ central nodes set it false.
Multi-stage Dockerfile with NuGet restore layer caching, per-node appsettings
with Docker hostnames, shared bridge network with infra services, and
build/deploy/teardown scripts. Ports use 90xx block to avoid conflicts.