Add multi-segment LED targets, replace single color strip source + skip fields

Each target now has a segments list where each segment maps a color strip
source to a pixel range (start/end) on the device with optional reverse.
This enables composing multiple visualizations on a single LED strip.
Old targets auto-migrate from the single source format on load.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/wled_controller/static/css/modal.css

@@ -231,6 +231,92 @@
     width: 100%;
 }
 
+/* Segment rows in target editor */
+.segment-row {
+    border: 1px solid var(--border-color, #333);
+    border-radius: 6px;
+    padding: 8px 10px;
+    margin-bottom: 6px;
+    background: var(--card-bg, #1e1e1e);
+}
+
+.segment-row-header {
+    display: flex;
+    justify-content: space-between;
+    align-items: center;
+    margin-bottom: 6px;
+}
+
+.segment-index-label {
+    font-size: 0.8rem;
+    font-weight: 600;
+    color: #888;
+}
+
+.btn-icon-inline {
+    background: none;
+    border: none;
+    cursor: pointer;
+    font-size: 1.1rem;
+    padding: 0 4px;
+    line-height: 1;
+}
+
+.btn-danger-text {
+    color: var(--danger-color, #f44336);
+}
+
+.btn-danger-text:hover {
+    color: #ff6659;
+}
+
+.segment-row-fields {
+    display: flex;
+    flex-wrap: wrap;
+    gap: 8px;
+    align-items: center;
+}
+
+.segment-row-fields select {
+    flex: 1 1 100%;
+}
+
+.segment-range-fields {
+    display: flex;
+    gap: 6px;
+    align-items: center;
+    flex: 1;
+}
+
+.segment-range-fields label {
+    font-size: 0.82rem;
+    color: #aaa;
+    white-space: nowrap;
+}
+
+.segment-range-fields input[type="number"] {
+    width: 70px;
+}
+
+.segment-reverse-label {
+    display: flex;
+    align-items: center;
+    gap: 4px;
+    font-size: 0.85rem;
+    color: #aaa;
+    cursor: pointer;
+    white-space: nowrap;
+}
+
+.segment-reverse-label input[type="checkbox"] {
+    margin: 0;
+}
+
+.btn-sm {
+    font-size: 0.85rem;
+    padding: 4px 10px;
+}
+
 .fps-hint {
     display: block;
     margin-top: 4px;