feat(anthrax-cat): add Maneki-neko lucky cat decoration addon, remove easter egg

- New silverlabs:anthrax_cat entity: sitting cat with waving paw animation,
  idle body bob, look-at-player, fortune message + bell sound on interact
- Custom 64x64 texture (cream/white, red bib, gold coin, orange tabby patches)
- Custom geometry: body, head, ears, raised left arm, tail, bib, coin bones
- Removed easter egg addon mounts from all 4 servers (lobby + 3 child worlds)
- Anthrax Cat mounted on all 4 servers

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

addon/anthrax_cat_RP/animations/anthrax_cat.animation.json

@@ -0,0 +1,40 @@
+{
+  "format_version": "1.8.0",
+  "animations": {
+    "animation.anthrax_cat.wave": {
+      "loop": true,
+      "animation_length": 2.0,
+      "bones": {
+        "left_arm": {
+          "rotation": {
+            "0.0":  [0, 0, 0],
+            "0.5":  [-25, 0, 0],
+            "1.0":  [0, 0, 0],
+            "1.5":  [-25, 0, 0],
+            "2.0":  [0, 0, 0]
+          }
+        }
+      }
+    },
+    "animation.anthrax_cat.idle": {
+      "loop": true,
+      "animation_length": 3.0,
+      "bones": {
+        "body": {
+          "position": {
+            "0.0": [0, 0, 0],
+            "1.5": [0, 0.3, 0],
+            "3.0": [0, 0, 0]
+          }
+        },
+        "head": {
+          "rotation": {
+            "0.0": [0, 3, 0],
+            "1.5": [0, -3, 0],
+            "3.0": [0, 3, 0]
+          }
+        }
+      }
+    }
+  }
+}