Fix blank portal: add root element heights, use dagre for graph layout

- Set explicit height on html/body/#root so React Flow container renders
- Replace @dagrejs/dagre (broken CJS dynamic require) with dagre v0.8.5
- Hierarchical top-down layout with dagre, arrow markers on edges
- Move React Flow controls to top-right to avoid floating button overlap

portal/package.json

@@ -10,7 +10,9 @@
   },
   "dependencies": {
     "@tanstack/react-query": "^5.62.0",
+    "@types/dagre": "^0.7.53",
     "@xyflow/react": "^12.4.0",
+    "dagre": "^0.8.5",
     "react": "^19.0.0",
     "react-dom": "^19.0.0"
   },
@@ -18,9 +20,9 @@
     "@tailwindcss/vite": "^4.0.0",
     "@types/react": "^19.0.0",
     "@types/react-dom": "^19.0.0",
+    "@vitejs/plugin-react": "^4.3.0",
     "tailwindcss": "^4.0.0",
     "typescript": "^5.9.0",
-    "vite": "^6.0.0",
-    "@vitejs/plugin-react": "^4.3.0"
+    "vite": "^6.0.0"
   }
 }