feat(web/panettone): Read config from env

Read the port and data directory from environment variables, in
preparation for deploying as a systemd unit to Whitby

Change-Id: I066dced7b7926b6bdc77132d13a4da6c886b20e8
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1338
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>

lisp/klatre/klatre.lisp

@@ -88,3 +88,9 @@ separated by SEP."
 
 (comment
  (format-dottime (local-time:now)))
+
+(defun try-parse-integer (str)
+  "Attempt to parse STR as an integer, returning nil if it is invalid."
+  (check-type str string)
+  (handler-case (parse-integer str)
+    (sb-int:simple-parse-error (_) nil)))

lisp/klatre/package.lisp

@@ -9,4 +9,5 @@
    #:chunk-list #:mapconcat
 
    ;; String handling
-   #:+dottime-format+ #:format-dottime))
+   #:+dottime-format+ #:format-dottime
+   #:try-parse-integer))