Add stream categorization: Recommended/Alternative with Main/Sub/Other subgroups

- Split discovered streams into Recommended (FFMPEG, ONVIF) and Alternative groups
- Add Main/Sub/Other classification within Recommended based on resolution:
  - Main: streams with width >= 720px (after clustering analysis)
  - Sub: streams with width < 720px or lower cluster
  - Other: streams without resolution info
- Implement smart auto-collapse based on selection mode:
  - Main selection: shows Recommended/Main, collapses rest
  - Sub selection: shows Recommended/Sub, collapses rest
  - Falls back to showing all if target category is empty
- Add collapsible groups/subgroups with chevron toggles
- User manual expand/collapse preserved until mode change
- Add stream count badges to all group headers

webui/web/css/main.css

@@ -590,10 +590,155 @@ body {
 .streams-list {
     display: flex;
     flex-direction: column;
-    gap: var(--space-3);
+    gap: var(--space-6);
     padding: var(--space-2);
 }
 
+/* ===== STREAM GROUPS ===== */
+.stream-group {
+    display: flex;
+    flex-direction: column;
+    gap: var(--space-3);
+}
+
+.stream-group-header {
+    display: flex;
+    align-items: center;
+    gap: var(--space-2);
+    padding-bottom: var(--space-2);
+    border-bottom: 1px solid var(--border-color);
+    cursor: pointer;
+    user-select: none;
+    transition: color var(--transition-fast);
+}
+
+.stream-group-header:hover {
+    color: var(--purple-primary);
+}
+
+.stream-group-toggle {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    background: none;
+    border: none;
+    padding: 0;
+    cursor: pointer;
+    color: var(--text-tertiary);
+    transition: all var(--transition-fast);
+}
+
+.stream-group-toggle .chevron {
+    transition: transform var(--transition-fast);
+}
+
+.stream-group.collapsed .stream-group-toggle .chevron {
+    transform: rotate(-90deg);
+}
+
+.stream-group.collapsed .stream-group-content {
+    display: none;
+}
+
+.stream-group-title {
+    font-size: var(--text-sm);
+    font-weight: 600;
+    color: var(--text-primary);
+    text-transform: uppercase;
+    letter-spacing: 0.05em;
+}
+
+.stream-group-count {
+    font-size: var(--text-sm);
+    font-weight: 400;
+    color: var(--text-tertiary);
+}
+
+.stream-group-content {
+    display: flex;
+    flex-direction: column;
+    gap: var(--space-3);
+}
+
+.stream-group-empty {
+    padding: var(--space-4);
+    text-align: center;
+    color: var(--text-tertiary);
+    font-size: var(--text-sm);
+    background: var(--bg-secondary);
+    border: 1px dashed var(--border-color);
+    border-radius: 8px;
+}
+
+/* ===== STREAM SUBGROUPS (Main/Sub/Other within Recommended) ===== */
+.stream-subgroup {
+    display: flex;
+    flex-direction: column;
+    gap: var(--space-2);
+}
+
+.stream-subgroup:not(:last-child) {
+    margin-bottom: var(--space-4);
+}
+
+.stream-subgroup-header {
+    display: flex;
+    align-items: center;
+    gap: var(--space-2);
+    padding-left: var(--space-2);
+    cursor: pointer;
+    user-select: none;
+    transition: color var(--transition-fast);
+}
+
+.stream-subgroup-header:hover {
+    color: var(--purple-primary);
+}
+
+.stream-subgroup-toggle {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    background: none;
+    border: none;
+    padding: 0;
+    cursor: pointer;
+    color: var(--text-tertiary);
+    transition: all var(--transition-fast);
+}
+
+.stream-subgroup-toggle .chevron {
+    transition: transform var(--transition-fast);
+}
+
+.stream-subgroup.collapsed .stream-subgroup-toggle .chevron {
+    transform: rotate(-90deg);
+}
+
+.stream-subgroup.collapsed .stream-subgroup-content {
+    display: none;
+}
+
+.stream-subgroup-title {
+    font-size: var(--text-xs);
+    font-weight: 500;
+    color: var(--text-tertiary);
+    text-transform: uppercase;
+    letter-spacing: 0.08em;
+}
+
+.stream-subgroup-count {
+    font-size: var(--text-xs);
+    font-weight: 400;
+    color: var(--text-disabled);
+}
+
+.stream-subgroup-content {
+    display: flex;
+    flex-direction: column;
+    gap: var(--space-2);
+}
+
 /* Custom scrollbar */
 .streams-list::-webkit-scrollbar {
     width: 8px;