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

ProjectSettings/NeedleExporterSceneData.asset

@@ -0,0 +1,27 @@
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+--- !u!114 &1
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+  m_PrefabInstance: {fileID: 0}
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+  m_Script: {fileID: 11500000, guid: 6aacfb80dc794b8ba5fd207d1da5c13a, type: 3}
+  m_Name: 
+  m_EditorClassIdentifier: Needle.Engine.Editor::Needle.Engine.Projects.ProjectsData
+  Scenes:
+  - Path: Assets/MenuScene.unity
+    Projects: []
+    BuilderScene: 
+  - Path: Assets/Scenes/SampleScene.unity
+    Projects: []
+    BuilderScene: 
+  - Path: Assets/Scenes/MenuScene.unity
+    Projects:
+    - ProjectPath: Needle/MenuScene
+    BuilderScene: 
+  Projects:
+  - ProjectPath: Needle/MenuScene