add rate limiting, CSRF, newsletter, auto-checker, /uses and /projects pages

.env.example

@@ -43,3 +43,11 @@ SESSION_SECRET=change-me-use-openssl-rand-hex-32
 # Email address that receives hire form submissions.
 # Requires a working local MTA (OpenSMTPD) listening on localhost:25.
 CONTACT_EMAIL=hire@ridgwaysystems.org
+
+# ------------------------------------------------------------------
+# Service checker
+# ------------------------------------------------------------------
+
+# How often (in minutes) to HTTP-check services with a check_url in status.json.
+# Default: 5
+CHECK_INTERVAL=5