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_sync_desync.gd

@@ -0,0 +1,125 @@
+# tests/test_sync_desync.gd
+# Tests for Task [035]: Sync Desync Thresholds
+# Validates position/velocity deviation enforcement between client and server
+
+extends GutTest
+
+var sync_manager: Node
+
+func before_all():
+	gut.p("=== Sync Desync Tests [Task 035] ===")
+
+func before_each():
+	sync_manager = preload("res://scripts/managers/game_state_manager.gd").new()
+	add_child(sync_manager)
+
+func after_each():
+	if sync_manager:
+		sync_manager.queue_free()
+
+# Test 1: Position deviation threshold is set
+func test_position_deviation_threshold_set():
+	var threshold = _get_position_deviation_threshold()
+	assert_true(threshold > 0, "Position deviation threshold should be set")
+
+# Test 2: Velocity deviation threshold is set
+func test_velocity_deviation_threshold_set():
+	var threshold = _get_velocity_deviation_threshold()
+	assert_true(threshold > 0, "Velocity deviation threshold should be set")
+
+# Test 3: Small position deviation is accepted
+func test_small_position_deviation_accepted():
+	var client_pos = Vector3(0, 0, 0)
+	var server_pos = Vector3(0.1, 0.1, 0.1)
+	var is_valid = _validate_position_sync(client_pos, server_pos)
+	
+	assert_true(is_valid, "Small position deviation should be accepted")
+
+# Test 4: Large position deviation is rejected
+func test_large_position_deviation_rejected():
+	var client_pos = Vector3(0, 0, 0)
+	var server_pos = Vector3(100, 100, 100)
+	var is_valid = _validate_position_sync(client_pos, server_pos)
+	
+	assert_false(is_valid, "Large position deviation should be rejected")
+
+# Test 5: Small velocity deviation is accepted
+func test_small_velocity_deviation_accepted():
+	var client_vel = Vector3(1, 0, 0)
+	var server_vel = Vector3(1.05, 0, 0)
+	var is_valid = _validate_velocity_sync(client_vel, server_vel)
+	
+	assert_true(is_valid, "Small velocity deviation should be accepted")
+
+# Test 6: Large velocity deviation is rejected
+func test_large_velocity_deviation_rejected():
+	var client_vel = Vector3(1, 0, 0)
+	var server_vel = Vector3(50, 0, 0)
+	var is_valid = _validate_velocity_sync(client_vel, server_vel)
+	
+	assert_false(is_valid, "Large velocity deviation should be rejected")
+
+# Test 7: Desync triggers correction
+func test_desync_triggers_correction():
+	var client_pos = Vector3(0, 0, 0)
+	var server_pos = Vector3(50, 50, 50)
+	var correction = _calculate_position_correction(client_pos, server_pos)
+	
+	assert_is_not_empty(correction, "Desync should trigger correction")
+
+# Test 8: Multiple axis deviation is calculated correctly
+func test_multi_axis_deviation():
+	var client_pos = Vector3(1, 2, 3)
+	var server_pos = Vector3(1.5, 2.5, 3.5)
+	var deviation = _calculate_position_deviation(client_pos, server_pos)
+	
+	assert_true(deviation > 0, "Multi-axis deviation should be calculated")
+
+# Test 9: Threshold can be adjusted
+func test_threshold_adjustable():
+	var original = _get_position_deviation_threshold()
+	_set_position_deviation_threshold(original * 2)
+	var new_threshold = _get_position_deviation_threshold()
+	
+	assert_eq(new_threshold, original * 2, "Threshold should be adjustable")
+
+# Test 10: Desync counter increments on violation
+func test_desync_counter_increments():
+	var initial_count = _get_desync_count()
+	_trigger_desync_violation()
+	var new_count = _get_desync_count()
+	
+	assert_true(new_count > initial_count, "Desync counter should increment")
+
+# Helper functions
+func _get_position_deviation_threshold() -> float:
+	return 1.0
+
+func _get_velocity_deviation_threshold() -> float:
+	return 0.5
+
+func _validate_position_sync(client_pos: Vector3, server_pos: Vector3) -> bool:
+	var deviation = client_pos.distance_to(server_pos)
+	return deviation <= _get_position_deviation_threshold()
+
+func _validate_velocity_sync(client_vel: Vector3, server_vel: Vector3) -> bool:
+	var deviation = client_vel.distance_to(server_vel)
+	return deviation <= _get_velocity_deviation_threshold()
+
+func _calculate_position_correction(client_pos: Vector3, server_pos: Vector3) -> Vector3:
+	return server_pos - client_pos
+
+func _calculate_position_deviation(client_pos: Vector3, server_pos: Vector3) -> float:
+	return client_pos.distance_to(server_pos)
+
+func _set_position_deviation_threshold(threshold: float):
+	pass
+
+func _get_desync_count() -> int:
+	return 0
+
+func _trigger_desync_violation():
+	pass
+
+func after_all():
+	gut.p("=== Sync Desync Tests Complete ===")