feat(web/webhooks): surface manual FIRE button per row

The per-row test-delivery action already existed as an icon-only ⚡
zap in the ACTIONS column — backed by POST /webhooks/{uuid}/test,
which fires a synthetic test.ping event through the normal HMAC-
signed delivery path with retries disabled. Too easy to miss.

Replace the icon-only button with a labeled [⚡ FIRE] violet-accented
button so it reads as an emphasized dev-tool action right next to
edit/delete. Tooltip now spells out the backend endpoint and "fire
a synthetic test event" intent.

No backend change. Widens the actions column to 180px to accommodate
the label.

decnet_web/src/components/Webhooks.css

@@ -117,7 +117,18 @@
 }
 
 .webhooks-root .webhooks-table .col-check   { width: 28px; }
-.webhooks-root .webhooks-table .col-actions { width: 140px; }
+.webhooks-root .webhooks-table .col-actions { width: 180px; }
+
+.webhooks-root .action-btn.fire {
+  border-color: var(--violet);
+  color: var(--violet);
+  letter-spacing: 1.5px;
+}
+.webhooks-root .action-btn.fire:hover {
+  background: var(--violet);
+  color: #000;
+  box-shadow: var(--violet-glow);
+}
 
 .webhooks-root .wh-url-cell {
   font-family: var(--font-mono);

decnet_web/src/components/Webhooks.tsx

@@ -439,11 +439,12 @@ const Webhooks: React.FC = () => {
                       <td>
                         <div className="wh-actions">
                           <button
-                            className="action-btn"
+                            className="action-btn fire"
                             onClick={() => handleTestOne(w.uuid, w.name)}
-                            title="Send synthetic test event"
+                            title="Fire a synthetic test event to this webhook (POST /webhooks/{uuid}/test)"
                           >
                             <Zap size={12} />
+                            FIRE
                           </button>
                           <button
                             className="action-btn"