chore: add project scaffolding, third-party assets and settings

- Terrain, Prefabs, Textures, Modelle (u. a. Lieferkarton-/Vibrations-
  Rohdaten in Assets/Data)
- Third-Party-Pakete: TextMesh Pro, Toby Fredson Foliage Engine, Sat
  Productions Street Lights, ProBuilder Data
- Neue Szene Boot.unity, Shop-Szenenordner
- Package-Manifest/Lock, ProjectSettings, Build-Profile, .slnx
- Doku: EDITOR_SETUP.md, INSTALL.md, TODO.md

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

ProjectSettings/Packages/com.unity.ai.assistant/Settings.json

@@ -0,0 +1,11 @@
+{
+    "CustomInstructionsGUID": "",
+    "CheckpointEnabled": false,
+    "GitInstanceTypeValue": 0,
+    "CustomGitPath": "",
+    "CheckpointRetentionWeeks": 2,
+    "PlanExecutionPromptDismissed": false,
+    "CheckpointDiscoveryBannerDismissed": false,
+    "CheckpointDiscoveryUserDisabled": false,
+    "CheckpointDiscoveryFlowStarted": false
+}