proxy: start intercept on IPv6 too

Template rule for transparent mode are not properly adapted,
but they are user-configurable so that's not a problem.

(cherry picked from commit af9fc279)

src/opnsense/service/templates/OPNsense/Proxy/squid.conf

@@ -5,6 +5,7 @@
 {% if helpers.exists('OPNsense.proxy.forward.transparentMode') and OPNsense.proxy.forward.transparentMode == '1' %}
 # transparent mode, listen on localhost
 http_port 127.0.0.1:{{ OPNsense.proxy.forward.port }} intercept
+http_port [::1]:{{ OPNsense.proxy.forward.port }} intercept
 {% endif %}
 
 # Setup listen configuration
@@ -32,6 +33,7 @@ http_access allow ftp
 {% if helpers.exists('OPNsense.proxy.forward.ftpTransparentMode') and OPNsense.proxy.forward.ftpTransparentMode == '1' %}
 # transparent mode, listen on localhost
 ftp_port 127.0.0.1:{{ OPNsense.proxy.forward.ftpPort }} intercept
+ftp_port [::1]:{{ OPNsense.proxy.forward.ftpPort }} intercept
 {% endif %}
 
 # Setup ftp proxy