Add graph editor filter, anchor-based positioning, and context docs

- Add name/kind/subtype filter bar with keyboard shortcut (F key)
- Filtered-out nodes get dimmed styling, nearly invisible on minimap
- Add anchor-based positioning for minimap and toolbar (remembers
  which corner element is closest to, maintains offset on resize)
- Fix minimap not movable after reload (_applyMinimapAnchor undefined)
- Fix ResizeObserver to use anchor system for both minimap and toolbar
- Add graph-editor.md context file and update frontend.md with graph sync notes
- Add filter i18n keys for en/ru/zh locales

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

server/src/wled_controller/static/css/graph-editor.css

@@ -678,6 +678,77 @@
     color: var(--text-muted);
 }
 
+/* ── Filter bar ── */
+
+.graph-filter {
+    position: absolute;
+    top: 12px;
+    left: 50%;
+    transform: translateX(-50%);
+    display: none;
+    align-items: center;
+    gap: 6px;
+    background: var(--bg-color);
+    border: 1px solid var(--border-color);
+    border-radius: 8px;
+    padding: 6px 10px;
+    z-index: 30;
+    box-shadow: 0 2px 8px rgba(0,0,0,0.15);
+    min-width: 260px;
+}
+
+.graph-filter.visible {
+    display: flex;
+}
+
+.graph-filter-icon {
+    flex-shrink: 0;
+    stroke: var(--text-muted);
+    fill: none;
+    stroke-width: 2;
+    stroke-linecap: round;
+    stroke-linejoin: round;
+}
+
+.graph-filter-input {
+    flex: 1;
+    border: none;
+    background: transparent;
+    color: var(--text-color);
+    font-size: 0.85rem;
+    outline: none;
+    min-width: 0;
+}
+
+.graph-filter-clear {
+    background: none;
+    border: none;
+    color: var(--text-muted);
+    font-size: 1.1rem;
+    cursor: pointer;
+    padding: 0 2px;
+    line-height: 1;
+}
+
+.graph-filter-clear:hover {
+    color: var(--text-color);
+}
+
+.graph-filter-btn.active {
+    color: var(--primary-color);
+}
+
+/* ── Filtered-out state ── */
+
+.graph-node.graph-filtered-out {
+    opacity: 0.12;
+    pointer-events: none;
+}
+
+.graph-edge.graph-filtered-out {
+    opacity: 0.06;
+}
+
 /* ── Loading overlay for relayout ── */
 
 /* ── Add entity menu ── */