Improve stream UI: grouped sections, full-size preview lightbox, and test redesign

- Separate Screen Capture and Processed streams into grouped sections with headers
- Remove redundant Type dropdown from stream modal (type inferred from add button)
- Add full-resolution image to test endpoints alongside thumbnails
- Add image lightbox with clickable preview for full-size viewing
- Move test results from modal into lightbox overlay with capture stats
- Apply postprocessing to both thumbnail and full image for processed streams
- Rename "Assigned Picture Stream" to "Picture Stream" in device settings
- Fix null reference errors from removed test result HTML elements

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

server/src/wled_controller/static/style.css

@@ -2045,6 +2045,131 @@ input:-webkit-autofill:focus {
     margin-right: 6px;
 }
 
+/* Stream group sections */
+.stream-group {
+    margin-bottom: 24px;
+}
+
+.stream-group:last-child {
+    margin-bottom: 0;
+}
+
+.stream-group-header {
+    display: flex;
+    align-items: center;
+    gap: 8px;
+    margin-bottom: 12px;
+    padding-bottom: 8px;
+    border-bottom: 2px solid var(--border-color);
+}
+
+.stream-group-icon {
+    font-size: 1.2rem;
+}
+
+.stream-group-title {
+    font-size: 1rem;
+    font-weight: 600;
+    color: var(--text-color);
+}
+
+.stream-group-count {
+    background: var(--border-color);
+    color: var(--text-secondary);
+    font-size: 0.75rem;
+    font-weight: 600;
+    padding: 2px 8px;
+    border-radius: 10px;
+    min-width: 20px;
+    text-align: center;
+}
+
+/* Image Lightbox */
+.lightbox {
+    display: none;
+    position: fixed;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+    background: rgba(0, 0, 0, 0.92);
+    z-index: 10000;
+    justify-content: center;
+    align-items: center;
+    cursor: zoom-out;
+}
+
+.lightbox.active {
+    display: flex;
+}
+
+.lightbox-content {
+    position: relative;
+    max-width: 95%;
+    max-height: 95%;
+    cursor: default;
+}
+
+.lightbox-content img {
+    max-width: 100%;
+    max-height: 90vh;
+    object-fit: contain;
+    border-radius: 4px;
+    display: block;
+}
+
+.lightbox-close {
+    position: absolute;
+    top: 16px;
+    right: 16px;
+    background: rgba(255, 255, 255, 0.15);
+    border: none;
+    color: white;
+    font-size: 1.5rem;
+    width: 40px;
+    height: 40px;
+    border-radius: 50%;
+    cursor: pointer;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    transition: background 0.2s;
+    z-index: 1;
+}
+
+.lightbox-close:hover {
+    background: rgba(255, 255, 255, 0.3);
+}
+
+.lightbox-stats {
+    position: absolute;
+    bottom: 8px;
+    left: 8px;
+    background: rgba(0, 0, 0, 0.7);
+    backdrop-filter: blur(8px);
+    color: white;
+    padding: 8px 14px;
+    border-radius: 6px;
+    font-size: 0.8rem;
+    display: flex;
+    gap: 16px;
+    flex-wrap: wrap;
+}
+
+.lightbox-stats .stat-item {
+    display: flex;
+    gap: 4px;
+    align-items: center;
+}
+
+.lightbox-stats .stat-item span {
+    opacity: 0.7;
+}
+
+.lightbox-stats .stat-item strong {
+    font-weight: 600;
+}
+
 /* Responsive adjustments */
 @media (max-width: 768px) {
     .templates-grid {