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/css/graph-editor.css

@@ -704,21 +704,66 @@
     left: 50%;
     transform: translateX(-50%);
     display: none;
-    align-items: center;
+    flex-direction: column;
     gap: 6px;
     background: var(--bg-color);
     border: 1px solid var(--border-color);
     border-radius: 8px;
-    padding: 6px 10px;
+    padding: 8px 10px;
     z-index: 30;
     box-shadow: 0 2px 8px rgba(0,0,0,0.15);
     min-width: 260px;
+    max-width: 480px;
 }
 
 .graph-filter.visible {
     display: flex;
 }
 
+.graph-filter-row {
+    display: flex;
+    align-items: center;
+    gap: 6px;
+    width: 100%;
+}
+
+.graph-filter-pills {
+    display: flex;
+    flex-wrap: wrap;
+    gap: 4px;
+    align-items: center;
+}
+
+.graph-filter-pill {
+    background: transparent;
+    border: 1px solid var(--pill-color, var(--border-color));
+    color: var(--pill-color, var(--text-muted));
+    border-radius: 12px;
+    padding: 2px 8px;
+    font-size: 0.7rem;
+    cursor: pointer;
+    white-space: nowrap;
+    transition: background 0.15s, color 0.15s;
+    line-height: 1.4;
+}
+
+.graph-filter-pill:hover {
+    background: color-mix(in srgb, var(--pill-color, var(--border-color)) 15%, transparent);
+}
+
+.graph-filter-pill.active {
+    background: var(--pill-color, var(--primary-color));
+    color: #fff;
+    border-color: var(--pill-color, var(--primary-color));
+}
+
+.graph-filter-sep {
+    width: 1px;
+    height: 16px;
+    background: var(--border-color);
+    margin: 0 2px;
+}
+
 .graph-filter-icon {
     flex-shrink: 0;
     stroke: var(--text-muted);