Add multi-site Caddy helpers and document usage

- add startup/shutdown scripts that render a Caddyfile from JSON config and run health checks

- add Python utilities and a sample sites.json for declarative multi-site configuration

- document the workflow and ignore generated Caddy state artifacts

- normalize double-quote style across challenge workflow controllers, nodes, and tests

api/models/challenge.py

@@ -88,4 +88,3 @@ class ChallengeAttempt(Base):
         nullable=False,
         server_default=sa.func.current_timestamp(),
     )
-

api/models/red_blue.py

@@ -111,4 +111,3 @@ class TeamPairing(Base):
         nullable=False,
         server_default=sa.func.current_timestamp(),
     )
-