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/zh.json

@@ -1722,5 +1722,19 @@
   "section.empty.sync_clocks": "暂无同步时钟。点击 + 添加。",
   "section.empty.cspt": "暂无 CSS 处理模板。点击 + 添加。",
   "section.empty.automations": "暂无自动化。点击 + 添加。",
-  "section.empty.scenes": "暂无场景预设。点击 + 添加。"
+  "section.empty.scenes": "暂无场景预设。点击 + 添加。",
+
+  "bulk.select": "选择",
+  "bulk.cancel": "取消",
+  "bulk.selected_count.one": "已选 {count} 项",
+  "bulk.selected_count.other": "已选 {count} 项",
+  "bulk.select_all": "全选",
+  "bulk.deselect_all": "取消全选",
+  "bulk.delete": "删除",
+  "bulk.start": "启动",
+  "bulk.stop": "停止",
+  "bulk.enable": "启用",
+  "bulk.disable": "禁用",
+  "bulk.confirm_delete.one": "删除 {count} 项？",
+  "bulk.confirm_delete.other": "删除 {count} 项？"
 }