feat(tray): add Config button to dashboard panel via open-config API

Adds POST /api/open-config endpoint that invokes configWindowFunc to
show the config window. Adds a gear-icon Config button to the dashboard
action-buttons row with a click handler that calls the endpoint.

Author: jung-thomas

cmd/sap-devs-tray/frontend/index.html

@@ -67,6 +67,7 @@
     <div class="action-buttons">
         <button type="button" class="fd-button fd-button--emphasized" id="btn-sync">&#8635; Sync Now</button>
         <button type="button" class="fd-button" id="btn-inject">&#8635; Inject Now</button>
+        <button type="button" class="fd-button" id="btn-config">&#9881; Config</button>
     </div>
 
     <script src="js/app.js"></script>

cmd/sap-devs-tray/frontend/js/app.js

@@ -215,6 +215,13 @@
             });
         }
 
+        var btnConfig = document.getElementById('btn-config');
+        if (btnConfig) {
+            btnConfig.addEventListener('click', function() {
+                fetch('/api/open-config?token=' + token, { method: 'POST' });
+            });
+        }
+
         fetchState();
         setInterval(fetchState, 30000);
     });