Add filter, add READMES

frontend/README.md

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+# Frontend (React + Vite) – WebGL Graph Renderer
+
+The frontend renders the snapshot from `/api/graph` using WebGL2:
+
+- Nodes are drawn as points
+- Edges are drawn as lines only when sufficiently zoomed in
+- Selection + neighbor highlighting is driven by backend “selection queries”
+
+## Run
+
+Via Docker Compose (recommended):
+
+```bash
+docker compose up --build frontend
+```
+
+Open: `http://localhost:5173`
+
+## Configuration
+
+- `VITE_BACKEND_URL` controls where `/api/*` is proxied (see `frontend/vite.config.ts`).
+
+## UI
+
+- Drag: pan
+- Scroll: zoom
+- Click: select/deselect nodes
+
+Buttons:
+
+- **Top-right:** selection query mode (controls how the backend expands “neighbors” for the current selection)
+- **Bottom-right:** graph query mode (controls which SPARQL edge set the backend uses to build the graph snapshot; switching reloads the graph)
+
+The available modes are discovered from the backend at runtime (`/api/selection_queries` and `/api/graph_queries`).
+
+## Rendering / limits
+
+The renderer uses a quadtree spatial index and draws only a subset when zoomed out:
+
+- Points:
+  - Per-frame cap: `MAX_DRAW = 2_000_000` (sampling over visible leaves)
+- Lines:
+  - Drawn only when fewer than ~20k nodes are “visible” (leaf AABB overlap with the camera frustum)
+
+Selected and “neighbor” nodes are drawn on top using index buffers.