feat(ai): agente IA interno con RAG sobre NAN + app web en /ai

- API: /api/ai/chat, /conversations, /documents con embeddings qwen3-embedding,
  coseno en SQLite, dedup por hash, historial de conversaciones
- Base de conocimiento semilla (6 docs, 36 chunks): catálogo DIAGONAL,
  propuestas del cotizador, créditos, proceso de venta, FAQ, privacidad
- App agente-ia (Vite/React/Tailwind, StudioBlank) servida en /ai/ vía nginx
- 21 tests nuevos (91/91 verdes)

apps/agente-ia/package.json

@@ -0,0 +1,27 @@
+{
+  "name": "agente-ia",
+  "private": true,
+  "version": "0.0.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "tsc -b && vite build",
+    "test": "vitest run",
+    "preview": "vite preview"
+  },
+  "dependencies": {
+    "@fontsource/inter": "^5.3.0",
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0"
+  },
+  "devDependencies": {
+    "@tailwindcss/vite": "^4.0.0",
+    "@types/react": "^19.0.2",
+    "@types/react-dom": "^19.0.2",
+    "@vitejs/plugin-react": "^4.3.4",
+    "tailwindcss": "^4.0.0",
+    "typescript": "~5.6.3",
+    "vite": "^6.0.7",
+    "vitest": "^2.1.8"
+  }
+}