feat: add per-layer LED range and collapsible layers to composite source

Composite layers now support optional start/end LED range (toggleable)
and reverse flag, making composite a superset of mapped source. Layers
are collapsible with animated expand/collapse and consistent 0.85rem
font sizing. Delete button restyled as ghost icon button.

Also includes minor dashboard CSS overflow fixes.

server/src/wled_controller/static/css/dashboard.css

@@ -119,6 +119,11 @@
     color: var(--primary-text-color);
 }
 
+.dashboard-target-info > div {
+    min-width: 0;
+    overflow: hidden;
+}
+
 .dashboard-target-name {
     font-size: 0.85rem;
     font-weight: 600;
@@ -130,6 +135,11 @@
     gap: 4px;
 }
 
+.dashboard-target-name-text {
+    overflow: hidden;
+    text-overflow: ellipsis;
+}
+
 .dashboard-card-link {
     cursor: pointer;
 }