Clean repo for open source release

Remove build artifacts, dev tool configs, unused dependencies,
and third-party source dumps. Add proper README, update .gitignore,
clean up Makefile.

src/main/resources/assets/tiedup/tiedup_items/test_handcuffs.json

@@ -0,0 +1,14 @@
+{
+  "type": "tiedup:bondage_item",
+  "display_name": "Data-Driven Handcuffs",
+  "model": "tiedup:models/gltf/v2/handcuffs/cuffs_prototype.glb",
+  "regions": ["ARMS"],
+  "pose_priority": 30,
+  "escape_difficulty": 100,
+  "lockable": true,
+  "icon": "tiedup:item/beam_cuffs",
+  "animation_bones": {
+    "idle": ["rightArm", "leftArm"],
+    "struggle": ["rightArm", "leftArm"]
+  }
+}