Unset TRUSTED_PROXIES trusts the RFC 1918 ranges (closes #119)

With TRUSTED_PROXIES unset, bin/entrypoint.sh gives nginx one
set_real_ip_from line for each of 10.0.0.0/8, 172.16.0.0/12 and
192.168.0.0/16, as sneak ruled on 2026-09-22 for every app. A list
replaces them, and set and empty trusts no proxy; each entry is checked
as before. The backend inside the container still trusts only
127.0.0.1/32. Both READMEs, nginx.conf and the comment in
script/frontend-viewport-test say the new default.

Model: opus-5-5

script/frontend-viewport-test

@@ -64,8 +64,9 @@ main() {
     # nginx.conf is a template: the image renders it over its own
     # default.conf, with the same port and limit bin/entrypoint.sh uses.
     # The empty file it includes trusts no proxy, as bin/entrypoint.sh
-    # writes it when TRUSTED_PROXIES is unset. nginx.conf also includes
-    # the security headers, so the page runs under the shipped policy.
+    # writes it when TRUSTED_PROXIES is set and empty. nginx.conf also
+    # includes the security headers, so the page runs under the shipped
+    # policy.
     docker run -d --rm --name "$SERVER" \
         --network "$NETWORK" --network-alias netwatch \
         -e PORT=8080 -e NGINX_ENVSUBST_FILTER='^PORT$' \