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_egg.json

@@ -0,0 +1,23 @@
+{
+  "format_version": "1.20.10",
+  "minecraft:recipe_shaped": {
+    "description": {
+      "identifier": "silverlabs:dragon_egg"
+    },
+    "tags": ["crafting_table"],
+    "pattern": [
+      " B ",
+      "AGA",
+      " A "
+    ],
+    "key": {
+      "B": { "item": "minecraft:blaze_powder" },
+      "A": { "item": "minecraft:amethyst_shard" },
+      "G": { "item": "minecraft:gold_ingot" }
+    },
+    "result": {
+      "item": "silverlabs:dragon_egg",
+      "count": 1
+    }
+  }
+}