feat: implement basic web app

frontend/package.json

@@ -16,6 +16,8 @@
     "typecheck": "tsc --noEmit"
   },
   "dependencies": {
+    "@langchain/core": "^1.1.15",
+    "@langchain/langgraph-sdk": "^1.5.3",
     "@radix-ui/react-collapsible": "^1.1.12",
     "@radix-ui/react-dialog": "^1.1.15",
     "@radix-ui/react-dropdown-menu": "^2.1.16",
@@ -28,25 +30,31 @@
     "@radix-ui/react-tooltip": "^1.2.8",
     "@radix-ui/react-use-controllable-state": "^1.2.2",
     "@t3-oss/env-nextjs": "^0.12.0",
+    "@tanstack/react-query": "^5.90.17",
+    "@types/hast": "^3.0.4",
     "@xyflow/react": "^12.10.0",
     "ai": "^6.0.33",
+    "best-effort-json-parser": "^1.2.1",
     "better-auth": "^1.3",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "cmdk": "^1.1.1",
     "embla-carousel-react": "^8.6.0",
+    "hast": "^1.0.0",
     "lucide-react": "^0.562.0",
     "motion": "^12.26.2",
     "nanoid": "^5.1.6",
-    "next": "^16.1.1",
+    "next": "^15.2.8",
     "next-themes": "^0.4.6",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",
     "shiki": "^3.21.0",
-    "streamdown": "^2.0.1",
+    "streamdown": "1.5.1",
     "tailwind-merge": "^3.4.0",
     "tokenlens": "^1.3.1",
+    "unist-util-visit": "^5.0.0",
     "use-stick-to-bottom": "^1.1.1",
+    "uuid": "^13.0.0",
     "zod": "^3.24.2"
   },
   "devDependencies": {