for #688: add PAGE_TOKEN_TIMER to .env-dist for CI

.env-dist

@@ -18,6 +18,9 @@ DATABASE_URL="postgres://postgres@localhost:5432/blurts"
 # How many seconds can unverified subscribers remain in the database
 DELETE_UNVERIFIED_SUBSCRIBERS_TIMER=86400
 
+# How many seconds until page tokens expire?
+PAGE_TOKEN_TIMER=0
+
 # Email server
 SMTP_URL=""
 # From: address used in emails