Add graph filter by entity type/running state and fix duplicate API calls

- Add entity type toggle pills and running/stopped filter to graph filter bar
- DataCache: return cached data if fresh, skip redundant fetches on page load
- Entity events: use force-fetch instead of invalidate+fetch to avoid stale gap
- Add no-cache middleware for static JS/CSS/JSON to prevent stale browser cache
- Reduces API calls on page load from ~70 to ~30

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

server/src/wled_controller/static/locales/zh.json

@@ -1414,5 +1414,7 @@
   "graph.color_picker": "节点颜色",
   "graph.filter": "筛选节点",
   "graph.filter_placeholder": "按名称筛选...",
-  "graph.filter_clear": "清除筛选"
+  "graph.filter_clear": "清除筛选",
+  "graph.filter_running": "运行中",
+  "graph.filter_stopped": "已停止"
 }