fix(slm): guard htmx.trigger so deploy/bench doesn't throw on pages without #slm-list

toggleSLMDeployed() and the save-config success path both called
htmx.trigger('#slm-list', 'load') guarded only by `typeof htmx !== 'undefined'`.
No page actually has a #slm-list element, so htmx resolved the selector to null
and called null.dispatchEvent(...) -> "can't access property dispatchEvent, e is
null". The deploy POST had already succeeded and the green success message had
already rendered, so the user saw both "Unit marked as deployed." and a red
error. Guard the trigger on the element existing so it's a harmless no-op.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

templates/partials/slm_settings_modal.html

@@ -528,7 +528,7 @@ async function saveSLMSettings(event) {
             if (typeof checkFTPStatus === 'function') {
                 checkFTPStatus(unitId);
             }
-            if (typeof htmx !== 'undefined') {
+            if (typeof htmx !== 'undefined' && document.getElementById('slm-list')) {
                 htmx.trigger('#slm-list', 'load');
             }
         }, 1500);
@@ -604,8 +604,10 @@ async function toggleSLMDeployed() {
         successDiv.classList.remove('hidden');
         setTimeout(() => successDiv.classList.add('hidden'), 3000);
 
-        // Refresh any SLM list on the page
-        if (typeof htmx !== 'undefined') {
+        // Refresh any SLM list on the page (only if one is actually present —
+        // the detail/dashboard pages have no #slm-list, and htmx.trigger on a
+        // null target throws "can't access property dispatchEvent, e is null").
+        if (typeof htmx !== 'undefined' && document.getElementById('slm-list')) {
             htmx.trigger('#slm-list', 'load');
         }
     } catch (error) {