fix: update .env.example and docker-compose.yml for CRON error and configuration clarity

.env.example

@@ -8,10 +8,11 @@ PA11Y_PORT=4000
 READONLY=false
 
 # Optional site message to display on homepage
-SITE_MESSAGE=Welcome to Pa11y Dashboard!
+SITE_MESSAGE=
 
 # Enable automatic testing with cron expression
-# Examples:
-#   0 2 * * *     = Daily at 2 AM
-#   0 */6 * * *   = Every 6 hours
-WEBSERVICE_CRON=false
+# Leave commented out to disable automatic testing
+# Uncomment and set to enable:
+# WEBSERVICE_CRON=0 2 * * *     # Daily at 2 AM
+# WEBSERVICE_CRON=0 */6 * * *   # Every 6 hours Configuration
+# Copy this file to .env and customize as needed