Fix: show real Stripe error in toast + add /billing/stripe-check endpoint

billing/index.tsx:
- Toast now shows actual backend detail message instead of hardcoded string
- Falls back to err.message then generic text if no detail
- duration: 6000ms so user can read the full error
- console.error logs the full error for debugging

billing.py:
- Add GET /api/billing/stripe-check endpoint
- Returns which env vars are set (secret key masked as bool, price IDs shown)
- Helps diagnose missing Render config without checking the dashboard

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: 2 people

backend/routes/billing.py

@@ -33,6 +33,19 @@ async def billing_status(current_user: Annotated[dict, Depends(get_current_user)
     return await get_subscription_status(user_id=current_user["id"])
 
 
+@router.get("/stripe-check")
+async def stripe_config_check(current_user: Annotated[dict, Depends(get_current_user)]):
+    """Return which Stripe env vars are configured (values masked)."""
+    from config import settings
+    return {
+        "STRIPE_SECRET_KEY":       bool(settings.STRIPE_SECRET_KEY),
+        "STRIPE_WEBHOOK_SECRET":   bool(settings.STRIPE_WEBHOOK_SECRET),
+        "STRIPE_PRO_PRICE_ID":     settings.pro_monthly_price_id or "NOT SET",
+        "STRIPE_AGENCY_PRICE_ID":  settings.agency_monthly_price_id or "NOT SET",
+        "FRONTEND_URL":            settings.FRONTEND_URL or "NOT SET",
+    }
+
+
 @router.post("/checkout")
 async def create_checkout(
     body: CheckoutRequest,

frontend/pages/billing/index.tsx

@@ -116,13 +116,11 @@ export default function BillingPage() {
       const { checkout_url } = await billingApi.createCheckoutSession(planId, 'monthly', priceId);
       window.location.href = checkout_url;
     } catch (err: unknown) {
-      const msg =
+      const detail =
         (err as { response?: { data?: { detail?: string } } })?.response?.data?.detail;
-      toast.error(
-        msg === 'No valid price_id or plan_id provided.'
-          ? 'Stripe is not configured. Set STRIPE_PRO_PRICE_ID / STRIPE_AGENCY_PRICE_ID in your backend .env.'
-          : 'Failed to start checkout. Please try again.'
-      );
+      const msg = detail || (err instanceof Error ? err.message : null);
+      toast.error(msg || 'Failed to start checkout. Please try again.', { duration: 6000 });
+      console.error('[checkout]', err);
       setLoadingPlan(null);
     }
   };