fix: free checkout requires Stripe SetupIntent for age verification; update copy

src/pricing.el

@@ -91,7 +91,7 @@ fn pricing(sold: Int, total: Int) -> String {
             el_span("class=\"pricing-price\"", "$0") +
             el_span("class=\"pricing-cadence\"", "forever")
         ) +
-        el_p("class=\"pricing-tagline\"", "Start building your memory. No card required.") +
+        el_p("class=\"pricing-tagline\"", "Start building your memory. Card required for age verification — you won't be charged.") +
         el_ul("class=\"pricing-features\"", pricing_free_features()) +
         el_div("style=\"flex:1\"", "") +
         el_div(