Card bulk operations, remove expand/collapse, graph color picker fix

- Bulk selection mode: Ctrl+Click or toggle button to enter, Escape to exit
- Shift+Click for range select, bottom toolbar with SVG icon action buttons
- All CardSections wired with bulk actions: Delete everywhere,
  Start/Stop for targets, Enable/Disable for automations
- Remove expand/collapse all buttons (no collapsible sections remain)
- Fix graph node color picker overlay persisting after outside click
- Add Icons section to frontend.md conventions
- Add trash2, listChecks, circleOff icons to icon system
- Backend: processing loop performance improvements (monotonic timestamps,
  deque-based FPS tracking)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/src/wled_controller/static/css/cards.css

@@ -267,8 +267,9 @@ body.cs-drag-active .card-drag-handle {
     opacity: 0 !important;
 }
 
-/* Hide drag handles when filter is active */
-.cs-filtering .card-drag-handle {
+/* Hide drag handles when filter is active or bulk selecting */
+.cs-filtering .card-drag-handle,
+.cs-selecting .card-drag-handle {
     display: none;
 }
 
@@ -1112,3 +1113,146 @@ ul.section-tip li {
 .led-preview-layers:hover .led-preview-layer-label {
     opacity: 1;
 }
+
+/* ── Bulk selection ────────────────────────────────────────── */
+
+/* Toggle button in section header */
+.cs-bulk-toggle {
+    background: none;
+    border: 1px solid var(--border-color);
+    color: var(--text-secondary);
+    font-size: 0.75rem;
+    width: 24px;
+    height: 24px;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    cursor: pointer;
+    border-radius: 4px;
+    transition: color 0.2s, background 0.2s, border-color 0.2s;
+    flex-shrink: 0;
+    line-height: 1;
+}
+
+.cs-bulk-toggle:hover {
+    border-color: var(--primary-color);
+    color: var(--primary-text-color);
+}
+
+.cs-bulk-toggle.active {
+    background: var(--primary-color);
+    border-color: var(--primary-color);
+    color: var(--primary-contrast, #fff);
+}
+
+/* Checkbox inside card — hidden unless selecting */
+.card-bulk-check {
+    display: none;
+    width: 16px;
+    height: 16px;
+    cursor: pointer;
+    accent-color: var(--primary-color);
+    flex-shrink: 0;
+}
+
+.cs-selecting .card-bulk-check {
+    display: block;
+}
+
+/* Selected card highlight */
+.cs-selecting .card-selected,
+.cs-selecting .card-selected.template-card {
+    border-color: var(--primary-color);
+    box-shadow: 0 0 0 1px var(--primary-color), 0 4px 12px color-mix(in srgb, var(--primary-color) 15%, transparent);
+}
+
+/* Make cards visually clickable in selection mode */
+.cs-selecting .card,
+.cs-selecting .template-card {
+    cursor: pointer;
+}
+
+/* Suppress hover lift during selection */
+.cs-selecting .card:hover,
+.cs-selecting .template-card:hover {
+    transform: none;
+}
+
+/* ── Bulk toolbar ──────────────────────────────────────────── */
+
+#bulk-toolbar {
+    position: fixed;
+    bottom: 20px;
+    left: 50%;
+    transform: translateX(-50%) translateY(calc(100% + 30px));
+    background: var(--card-bg);
+    border: 1px solid var(--border-color);
+    border-radius: var(--radius-md, 8px);
+    padding: 8px 16px;
+    display: flex;
+    align-items: center;
+    gap: 12px;
+    z-index: 1000;
+    box-shadow: 0 -4px 24px rgba(0, 0, 0, 0.3);
+    transition: transform 0.25s ease;
+    white-space: nowrap;
+}
+
+#bulk-toolbar.visible {
+    transform: translateX(-50%) translateY(0);
+}
+
+.bulk-select-all-wrap {
+    display: flex;
+    align-items: center;
+    cursor: pointer;
+}
+
+.bulk-select-all-cb {
+    width: 16px;
+    height: 16px;
+    margin: 0;
+    accent-color: var(--primary-color);
+    cursor: pointer;
+}
+
+.bulk-count {
+    font-size: 0.85rem;
+    color: var(--text-secondary);
+    min-width: 80px;
+}
+
+.bulk-actions {
+    display: flex;
+    gap: 4px;
+}
+
+.bulk-action-btn {
+    width: 32px;
+    height: 32px;
+    padding: 0;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+}
+
+.bulk-action-btn .icon {
+    width: 16px;
+    height: 16px;
+}
+
+.bulk-close {
+    background: none;
+    border: none;
+    color: var(--text-muted);
+    font-size: 1rem;
+    cursor: pointer;
+    padding: 4px;
+    border-radius: 4px;
+    transition: color 0.2s;
+    line-height: 1;
+}
+
+.bulk-close:hover {
+    color: var(--text-color);
+}