feat: add multi-world hub system with lobby portals and hub-return addon

Lobby addon detects players in portal zones at X: -15/0/15 and transfers
them to Jamie/Lyla/Mya survival worlds. Hub-return addon gives players a
recovery compass and chat commands (!hub, !lobby) to return to the lobby.

Includes docker-compose.yml for 4 Bedrock servers (lobby + 3 child worlds),
spark pet behavior/resource packs, and updated .gitignore.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

addon/spark_pet_BP/recipes/dragon_basket.json

@@ -0,0 +1,22 @@
+{
+  "format_version": "1.21.0",
+  "minecraft:recipe_shaped": {
+    "description": {
+      "identifier": "silverlabs:dragon_basket_recipe"
+    },
+    "tags": ["crafting_table"],
+    "pattern": [
+      "S S",
+      "WLW",
+      "SSS"
+    ],
+    "key": {
+      "S": { "item": "minecraft:stick" },
+      "W": { "item": "minecraft:wool" },
+      "L": { "item": "minecraft:leather" }
+    },
+    "result": {
+      "item": "silverlabs:dragon_basket"
+    }
+  }
+}