Set up a second snowflake bridge site

At #28651 (closed), the plan is to run more than one snowflake bridge site. Each bridge site will have one instance of snowflake-server, speaking to a group of tor instances that all have the same identity keys. The identity keys in different bridge sites will be different. Until now, we have had only one bridge site, and have kept the tor identity keys the same through server migrations (#40091 (closed), #40095 (closed), #40110 (closed), #40111 (closed)). This issue is to set up a second bridge site, with its own, independent identity keys.

• get access to the server hardware
• decide on a bridge nickname
• install bridge software (installation guide)
• set up user accounts #40091 (comment 2768855)
• point a domain name at the server #28651 (comment 2787394)
• disable plain SSH access

/cc @shelikhoo