Initial commit: Unity Needle AR Menu project with MenuScene and SampleScene web apps

Add root .gitignore for Unity Library/Temp/Logs, IDE folders, and node_modules.
Include Assets, Needle TypeScript (MenuController, asset picker, WebXR), and project configuration.

Made-with: Cursor

Needle/SampleScene/needle.config.json

@@ -0,0 +1,7 @@
+{
+  "baseUrl": null,
+  "buildDirectory": "dist",
+  "assetsDirectory": "assets",
+  "scriptsDirectory": "src/scripts",
+  "codegenDirectory": "src/generated"
+}