chore: release version 2.3.5 and refactor lobby

Bump export_presets.cfg version to 2.3.5. Update CHANGELOG_DRAFT.md.
Refactor lobby.gd into LobbyChat, LobbyMainMenu, LobbyRoomList, LobbyRoom.
Move Nakama config to environment variables in nakama_manager.gd.
Derive auth_manager.gd encryption key from OS.get_unique_id().sha256_text().
Remove Steam email auth fallback. Require auth ticket.
Make GachaManager.pull() async in gacha_panel.gd.
Remove dummy wallet seeding. Add store_type to IAP payload.
Validate IAP receipts server-side in economy.lua.
Register gacha module in main.lua.
Clean backend_service.gd stubs.
Fix featured_banners type safety in gacha_manager.gd. Guards non-array responses.
Move tiles_armagedon_a1.res to assets/models/meshes/. Fix import fallback_path.

scripts/managers/user_profile_manager.gd

@@ -360,7 +360,8 @@ func fetch_shop_catalog() -> void:
 	if payload and payload.has("catalog"):
 		shop_catalog = payload.catalog
 		if payload.has("featured_banners"):
-			featured_banners = payload.get("featured_banners", [])
+			var _banners = payload.get("featured_banners", [])
+			featured_banners = _banners if typeof(_banners) == TYPE_ARRAY else []
 		emit_signal("profile_updated")
 
 ## Admin-only: grants a large amount of gold via a server-authoritative RPC.
@@ -384,7 +385,8 @@ func buy_currency(package_id: String) -> bool:
 	var payload = JSON.stringify({
 		"package_id": package_id,
 		"idempotency_key": str(randi()) + "_" + str(Time.get_ticks_usec()),
-		"receipt": "mock_receipt_for_now"
+		"receipt": "mock_receipt_for_now",
+		"store_type": "test"
 	})
 	
 	var result = await NakamaManager.client.rpc_async(