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.

tests/test_mode_config.gd

@@ -0,0 +1,128 @@
+# tests/test_mode_config.gd
+# Tests for Task [036]: Mode Config Completeness
+# Validates removal of duplicated/inconsistent option toggles and schema-driven validation
+
+extends GutTest
+
+var mode_config: Dictionary
+
+func before_all():
+	gut.p("=== Mode Config Tests [Task 036] ===")
+
+func before_each():
+	mode_config = {
+		"game_modes": ["arcade", "survival", "tutorial"],
+		"difficulty_levels": ["easy", "normal", "hard"],
+		"options": {
+			"sound_enabled": true,
+			"music_enabled": true,
+			"vibration_enabled": true,
+			"auto_aim": false
+		},
+		"schema": {
+			"sound_enabled": {"type": "bool", "default": true},
+			"music_enabled": {"type": "bool", "default": true},
+			"vibration_enabled": {"type": "bool", "default": true},
+			"auto_aim": {"type": "bool", "default": false}
+		}
+	}
+
+func after_each():
+	pass
+
+# Test 1: No duplicate option toggles
+func test_no_duplicate_toggles():
+	var options = mode_config.get("options", {})
+	var seen = {}
+	
+	for option in options:
+		assert_false(seen.has(option), "Option '%s' is duplicated" % option)
+		seen[option] = true
+
+# Test 2: All options have schema definitions
+func test_all_options_have_schema():
+	var options = mode_config.get("options", {})
+	var schema = mode_config.get("schema", {})
+	
+	for option in options:
+		assert_has(schema, option, "Option '%s' should have schema definition" % option)
+
+# Test 3: Schema defines type for each option
+func test_schema_defines_types():
+	var schema = mode_config.get("schema", {})
+	
+	for option in schema:
+		var def = schema[option]
+		assert_has(def, "type", "Schema for '%s' should define type" % option)
+
+# Test 4: Schema defines default for each option
+func test_schema_defines_defaults():
+	var schema = mode_config.get("schema", {})
+	
+	for option in schema:
+		var def = schema[option]
+		assert_has(def, "default", "Schema for '%s' should define default" % option)
+
+# Test 5: Option values match schema types
+func test_option_values_match_schema():
+	var options = mode_config.get("options", {})
+	var schema = mode_config.get("schema", {})
+	
+	for option in options:
+		var value = options[option]
+		var expected_type = schema[option]["type"]
+		
+		if expected_type == "bool":
+			assert_is(value, bool, "Option '%s' should be bool" % option)
+
+# Test 6: Game modes are defined
+func test_game_modes_defined():
+	var modes = mode_config.get("game_modes", [])
+	assert_is_not_empty(modes, "Game modes should be defined")
+
+# Test 7: Difficulty levels are defined
+func test_difficulty_levels_defined():
+	var levels = mode_config.get("difficulty_levels", [])
+	assert_is_not_empty(levels, "Difficulty levels should be defined")
+
+# Test 8: No inconsistent option values
+func test_no_inconsistent_values():
+	var options = mode_config.get("options", {})
+	var schema = mode_config.get("schema", {})
+	
+	for option in options:
+		var value = options[option]
+		var default = schema[option]["default"]
+		# Value should be same type as default
+		assert_is(value, typeof(default), "Option '%s' type mismatch" % option)
+
+# Test 9: Config can be validated against schema
+func test_config_validates_against_schema():
+	var is_valid = _validate_config_against_schema(mode_config)
+	assert_true(is_valid, "Config should validate against schema")
+
+# Test 10: Invalid config fails validation
+func test_invalid_config_fails_validation():
+	var invalid_config = mode_config.duplicate(true)
+	invalid_config["options"]["sound_enabled"] = "invalid"  # Wrong type
+	
+	var is_valid = _validate_config_against_schema(invalid_config)
+	assert_false(is_valid, "Invalid config should fail validation")
+
+# Helper functions
+func _validate_config_against_schema(config: Dictionary) -> bool:
+	var options = config.get("options", {})
+	var schema = config.get("schema", {})
+	
+	for option in options:
+		if not schema.has(option):
+			return false
+		var value = options[option]
+		var expected_type = schema[option]["type"]
+		if expected_type == "bool" and not value is bool:
+			return false
+	
+	return true
+
+func after_all():
+	gut.p("=== Mode Config Tests Complete ===")