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/locales/en.json

@@ -1722,5 +1722,19 @@
   "section.empty.sync_clocks": "No sync clocks yet. Click + to add one.",
   "section.empty.cspt": "No CSS processing templates yet. Click + to add one.",
   "section.empty.automations": "No automations yet. Click + to add one.",
-  "section.empty.scenes": "No scene presets yet. Click + to add one."
+  "section.empty.scenes": "No scene presets yet. Click + to add one.",
+
+  "bulk.select": "Select",
+  "bulk.cancel": "Cancel",
+  "bulk.selected_count.one": "{count} selected",
+  "bulk.selected_count.other": "{count} selected",
+  "bulk.select_all": "Select all",
+  "bulk.deselect_all": "Deselect all",
+  "bulk.delete": "Delete",
+  "bulk.start": "Start",
+  "bulk.stop": "Stop",
+  "bulk.enable": "Enable",
+  "bulk.disable": "Disable",
+  "bulk.confirm_delete.one": "Delete {count} item?",
+  "bulk.confirm_delete.other": "Delete {count} items?"
 }