feat: added drag and drop menu for adding new nodes to flow

added a sidebar that supports drag and dropping new nodes from the sidebar into the flow editor.
also added a new package (neodrag) for easy draggable behavior outside the reactFlow editor.

ref: N25B-114

package-lock.json

@@ -8,6 +8,7 @@
       "name": "pepperplus-ui",
       "version": "0.0.0",
       "dependencies": {
+        "@neodrag/react": "^2.3.1",
         "@xyflow/react": "^12.8.6",
         "react": "^19.1.1",
         "react-dom": "^19.1.1"
@@ -1006,6 +1007,12 @@
         "@jridgewell/sourcemap-codec": "^1.4.14"
       }
     },
+    "node_modules/@neodrag/react": {
+      "version": "2.3.1",
+      "resolved": "https://registry.npmjs.org/@neodrag/react/-/react-2.3.1.tgz",
+      "integrity": "sha512-mOVefo3mFmaVLs9PB5F5wMXnnclG81qjOaPHyf8YZUnw/Ciz0pAqyJDwDJk0nPTIK5I2x1JdjXSchGNdCxZNRQ==",
+      "license": "MIT"
+    },
     "node_modules/@nodelib/fs.scandir": {
       "version": "2.1.5",
       "resolved": "https://registry.npmjs.org/@nodelib/fs.scandir/-/fs.scandir-2.1.5.tgz",