admin: remove Scheduler Settings cards, make Next Run full-width

Remove the two "Scheduler Settings" placeholder cards from the plugin
UI (overview page and scheduler tab). They only contained a text note
saying detection intervals are configured per job type, which is
self-evident from the per-job-type settings form.

Make the "Next Run" card full-width on the overview page since it no
longer shares a row with the removed card.

weed/admin/view/app/plugin.templ

@@ -149,19 +149,8 @@ templ Plugin(page string) {
                 </div>
             </div>
             <div class="row mb-4">
-                <div class="col-lg-6 mb-3">
-                    <div class="card shadow-sm h-100">
-                        <div class="card-header d-flex justify-content-between align-items-center">
-                            <h5 class="mb-0"><i class="fas fa-sliders-h me-2"></i>Scheduler Settings</h5>
-                            <small class="text-muted">Global</small>
-                        </div>
-                        <div class="card-body">
-                            <p class="text-muted mb-0">Detection intervals are configured per job type in the job type settings below.</p>
-                        </div>
-                    </div>
-                </div>
-                <div class="col-lg-6 mb-3">
-                    <div class="card shadow-sm h-100">
+                <div class="col-12 mb-3">
+                    <div class="card shadow-sm">
                         <div class="card-header d-flex justify-content-between align-items-center">
                             <h5 class="mb-0"><i class="fas fa-hourglass-half me-2"></i>Next Run</h5>
                             <small class="text-muted">Scheduler</small>
@@ -304,15 +293,6 @@ templ Plugin(page string) {
                         </div>
                     </div>
 
-                    <div class="card shadow-sm mt-3">
-                        <div class="card-header">
-                            <h5 class="mb-0"><i class="fas fa-clock me-2"></i>Scheduler Settings</h5>
-                        </div>
-                        <div class="card-body">
-                            <p class="text-muted mb-0">Detection intervals are configured per job type in the settings above.</p>
-                        </div>
-                    </div>
-
                     <div class="card shadow-sm mt-3">
                         <div class="card-header d-flex justify-content-between align-items-center">
                             <h5 class="mb-0"><i class="fas fa-hourglass-half me-2"></i>Next Run</h5>