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.

addons/gut/double_tools.gd

@@ -0,0 +1,83 @@
+var thepath = ''
+var subpath = ''
+var singleton_name = null
+var is_partial = null
+
+var double_ref : WeakRef = null
+var stubber_ref : WeakRef = null
+var spy_ref : WeakRef = null
+var gut_ref : WeakRef = null
+var singleton_ref : WeakRef = null
+var __gutdbl_values = {}
+
+const NO_DEFAULT_VALUE = '!__gut__no__default__value__!'
+func _init(double = null):
+	if(double != null):
+		var values = double.__gutdbl_values
+		__gutdbl_values = double.__gutdbl_values
+		double_ref = weakref(double)
+		thepath = values.thepath
+		subpath = values.subpath
+		stubber_ref = weakref_from_id(values.stubber)
+		spy_ref = weakref_from_id(values.spy)
+		gut_ref = weakref_from_id(values.gut)
+		singleton_ref = weakref_from_id(values.singleton)
+		singleton_name = values.singleton_name
+		is_partial = values.is_partial
+
+		if(gut_ref.get_ref() != null):
+			gut_ref.get_ref().get_autofree().add_free(double_ref.get_ref())
+
+
+func _get_stubbed_method_to_call(method_name, called_with):
+	var method = stubber_ref.get_ref().get_call_this(double_ref.get_ref(), method_name, called_with)
+	if(method != null):
+		method = method.bindv(called_with)
+		return method
+	return method
+
+
+func weakref_from_id(inst_id):
+	if(inst_id ==  -1):
+		return weakref(null)
+	else:
+		return weakref(instance_from_id(inst_id))
+
+
+func is_stubbed_to_call_super(method_name, called_with):
+	if(stubber_ref.get_ref() != null):
+		return stubber_ref.get_ref().should_call_super(double_ref.get_ref(), method_name, called_with)
+	else:
+		return false
+
+
+func handle_other_stubs(method_name, called_with):
+	if(stubber_ref.get_ref() == null):
+		return
+
+	var method = _get_stubbed_method_to_call(method_name, called_with)
+	if(method != null):
+		return await method.call()
+	else:
+		return stubber_ref.get_ref().get_return(double_ref.get_ref(), method_name, called_with)
+
+
+func spy_on(method_name, called_with):
+	if(spy_ref.get_ref() != null):
+		spy_ref.get_ref().add_call(double_ref.get_ref(), method_name, called_with)
+
+
+func default_val(method_name, p_index):
+	if(stubber_ref.get_ref() == null):
+		return null
+	else:
+		var result = stubber_ref.get_ref().get_default_value(double_ref.get_ref(), method_name, p_index)
+		return result
+
+
+func get_singleton():
+	var to_return = singleton_ref.get_ref()
+	if(to_return == null):
+		push_error("Trying to get a singleton reference on a non-singleton double: ",
+			__gutdbl_values.singleton_name, "/", __gutdbl_values.singleton)
+	return to_return