feat: componente GraphContainer con sigma.js y graphology

Visualizacion interactiva de grafos con WebGL via sigma.js, estructura de
datos graphology, y layout ForceAtlas2 adaptativo. Soporta grafos dirigidos
multi-edge, leyenda de tipos de nodo, y eventos click/double-click.
Nuevas deps: graphology, sigma, recharts.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/package.json

@@ -18,10 +18,15 @@
     "@fontsource-variable/geist": "^5.2.8",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
+    "graphology": "^0.26.0",
+    "graphology-layout-forceatlas2": "^0.10.1",
+    "graphology-types": "^0.24.8",
     "lucide-react": "^1.7.0",
     "react": "^19.2.4",
     "react-dom": "^19.2.4",
+    "recharts": "^3.8.1",
     "shadcn": "^4.1.1",
+    "sigma": "^3.0.2",
     "tailwind-merge": "^3.5.0",
     "tw-animate-css": "^1.4.0"
   },