add hostname helper

.devcontainer/Dockerfile

@@ -1,5 +1,2 @@
 ARG VARIANT="3.4.2"
 FROM ghcr.io/rails/devcontainer/images/ruby:${VARIANT}
-
-RUN mkdir /run/kubernaut && \
-    chown vscode: /run/kubernaut

app.rb

@@ -25,7 +25,8 @@ SESSION_SECRET_HEX_LENGTH = 64
 JWT_SECRET_HEX_LENGTH = 64
 DEFAULT_FLAKEY = 50
 
-ENV_PREFIX = "KUBERNAUT"
+NAME = "kubernaut".freeze
+ENV_PREFIX = NAME.upcase
 
 CLK_TCK = 100
 PROC_UPTIME_PATH = "/proc/uptime".freeze
@@ -279,6 +280,10 @@ helpers do
       @auth.credentials and
       @auth.credentials == ["qwer", "asdf"]
   end
+
+  def hostname
+    ENV["HOSTNAME"]
+  end
 end
 
 get "/" do