fix(dashboard): show paid-until-date when subscription is cancelled (#9)

Cancellation in this product is not a self-serve action — users
revoke their auto-pay mandate at the bank or directly inside
Razorpay. That fires subscription.cancelled to us, and our handler
stores current_period_end along with the cancelled status. The
cancellation email already tells the user "Paid access continues
until 2026-05-24" but the in-app banner just said "Cancellation
is in progress." — leaving the date as a thing they'd have to
re-derive from the email.

Banner now reads
  Paid access continues until May 24, 2026. After that you're
  back on the free tier.

Falls back to the old generic text when current_period_end isn't
populated (rare — happens if Razorpay didn't send current_end on
the cancel webhook). Date formatted via toLocaleDateString in the
visitor's locale.

No API change, no schema change, ~10 lines.

Author: mastermanas805

dashboard.html

@@ -401,13 +401,27 @@ <h2 id="apikey-heading">API token for CLI / agent</h2>
         return;
       }
 
-      // Paid-tier banner is a tight utility strip. Cancellation is intentionally
-      // NOT self-serve — the support email lives in the footer; users who want
-      // to cancel will find it and the operator processes the request manually.
+      // Paid-tier banner is a tight utility strip. Cancellation is NOT a
+      // self-serve action in this product — the user revokes their auto-pay
+      // mandate at their bank or in Razorpay, Razorpay fires
+      // subscription.cancelled to us, our handler stores the cancellation
+      // along with current_period_end. We display the resulting state.
       var variant = status === 'halted' ? 'warn' : 'paid';
       var tagText = status === 'halted' ? 'PAYMENT HALTED' : (status === 'cancelled' ? 'CANCELLING' : 'ACTIVE');
+      // For 'cancelled', show the until-date prominently when we have it —
+      // matches what the cancellation email already says, so users see the
+      // same guarantee in-app and don't lose track of when free-tier kicks in.
+      var periodEndDate = '';
+      if (plan.current_period_end) {
+        var d = new Date(plan.current_period_end);
+        if (!isNaN(d.getTime())) {
+          periodEndDate = d.toLocaleDateString(undefined, { year: 'numeric', month: 'short', day: 'numeric' });
+        }
+      }
       var subText = status === 'cancelled'
-        ? 'Cancellation is in progress.'
+        ? (periodEndDate
+            ? 'Paid access continues until ' + periodEndDate + '. After that you\'re back on the free tier.'
+            : 'Cancellation is in progress.')
         : (status === 'halted'
             ? 'Your card was declined. Update it and retry from the pricing page.'
             : 'Your plan is active. Resources are permanent.');