feat(portals): add craftable portal blocks replacing hardcoded coordinates

Portal frame crafted from obsidian + ender pearl, combined with crystals
(emerald/amethyst/prismarine) to create world-specific portal blocks.
Stepping on a portal block triggers transfer. Includes resource pack with
vanilla textures, block definitions, crafting recipes, and updated script.

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

lobby-addon/lobby_transfer_RP/manifest.json

@@ -0,0 +1,17 @@
+{
+  "format_version": 2,
+  "header": {
+    "name": "Lobby Portal Transfer Resources",
+    "description": "Textures and lang for craftable portal blocks",
+    "uuid": "b2c3d4e5-1111-2222-3333-fedcba654321",
+    "version": [1, 0, 0],
+    "min_engine_version": [1, 21, 0]
+  },
+  "modules": [
+    {
+      "type": "resources",
+      "uuid": "b2c3d4e5-4444-5555-6666-fedcba987654",
+      "version": [1, 0, 0]
+    }
+  ]
+}