Pass promo code through compliance checker to order page

- Compliance checker reads ?code= from URL, stores it, passes it
  through to the order page CTA link
- Allows email campaigns to link to checker with coupon pre-applied

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

site/src/pages/tools/fcc-compliance-check.astro

@@ -225,6 +225,9 @@ import Base from "../../layouts/Base.astro";
     // Race condition guard — cancel prior fetch when new one starts
     let currentController = null;
 
+    // Promo code passthrough from URL (e.g. ?code=MEMORIAL25)
+    let urlPromoCode = "";
+
     // --- Name search ---
     nameSearchBtn?.addEventListener("click", runNameSearch);
     nameInput?.addEventListener("keydown", (e) => { if (e.key === "Enter") runNameSearch(); });
@@ -1026,7 +1029,7 @@ import Base from "../../layouts/Base.astro";
           // Update link
           const btn = document.getElementById("get-started-btn");
           if (btn) {
-            btn.href = `/order/fcc-compliance?services=${selectedIds.join(",")}&frn=${frn}`;
+            btn.href = `/order/fcc-compliance?services=${selectedIds.join(",")}&frn=${frn}${urlPromoCode ? "&code=" + encodeURIComponent(urlPromoCode) : ""}`;
           }
         }
 
@@ -1130,6 +1133,7 @@ import Base from "../../layouts/Base.astro";
       const params = new URLSearchParams(window.location.search);
       const frn = params.get("frn");
       const entity = params.get("entity");
+      urlPromoCode = params.get("code") || params.get("promo") || "";
 
       if (frn) {
         frnInput.value = frn;