docs: expire stale ad click ids before sending conversions to the worker

docs-src/src/components/trigger-event.tsx

@@ -36,6 +36,15 @@ const CONVERSION_WORKER_URL = 'https://rxdb-events.daniel-meyer-e90.workers.dev'
  */
 export const AD_CLICK_STORAGE_ID = 'click_id';
 
+/**
+ * Google Ads' maximum click-through conversion window is 90 days. A stored
+ * click id older than that can never be imported ("this click is too old"),
+ * and attributing a later (often organic) visit to a months-old ad click would
+ * be wrong anyway. So we ignore (and clear) stale ids instead of uploading
+ * conversions against them forever.
+ */
+const AD_CLICK_MAX_AGE_MS = 90 * 24 * 60 * 60 * 1000;
+
 function getStoredAdClickId(): { k: string; v: string; t: number; } | null {
     try {
         const raw = localStorage.getItem(AD_CLICK_STORAGE_ID);
@@ -46,6 +55,10 @@ function getStoredAdClickId(): { k: string; v: string; t: number; } | null {
         if (!parsed || !parsed.v) {
             return null;
         }
+        if (typeof parsed.t !== 'number' || Date.now() - parsed.t > AD_CLICK_MAX_AGE_MS) {
+            localStorage.removeItem(AD_CLICK_STORAGE_ID);
+            return null;
+        }
         return parsed;
     } catch (err) {
         return null;