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/diff_formatter.gd

@@ -0,0 +1,63 @@
+var _strutils = GutUtils.Strutils.new()
+const INDENT = '    '
+var _max_to_display = 30
+const ABSOLUTE_MAX_DISPLAYED = 10000
+const UNLIMITED = -1
+
+
+func _single_diff(diff, depth=0):
+	var to_return = ""
+	var brackets = diff.get_brackets()
+
+	if(brackets != null and !diff.are_equal):
+		to_return = ''
+		to_return += str(brackets.open, "\n",
+			_strutils.indent_text(differences_to_s(diff.differences, depth), depth+1, INDENT), "\n",
+			brackets.close)
+	else:
+		to_return = str(diff)
+
+	return to_return
+
+
+func make_it(diff):
+	var to_return = ''
+	if(diff.are_equal):
+		to_return = diff.summary
+	else:
+		if(_max_to_display ==  ABSOLUTE_MAX_DISPLAYED):
+			to_return = str(diff.get_value_1(), ' != ', diff.get_value_2())
+		else:
+			to_return = diff.get_short_summary()
+		to_return +=  str("\n", _strutils.indent_text(_single_diff(diff, 0), 1, '  '))
+	return to_return
+
+
+func differences_to_s(differences, depth=0):
+	var to_return = ''
+	var keys = differences.keys()
+	keys.sort()
+	var limit = min(_max_to_display, differences.size())
+
+	for i in range(limit):
+		var key = keys[i]
+		to_return += str(key, ":  ", _single_diff(differences[key], depth))
+
+		if(i != limit -1):
+			to_return += "\n"
+
+	if(differences.size() > _max_to_display):
+		to_return += str("\n\n... ", differences.size() - _max_to_display, " more.")
+
+	return to_return
+
+
+func get_max_to_display():
+	return _max_to_display
+
+
+func set_max_to_display(max_to_display):
+	_max_to_display = max_to_display
+	if(_max_to_display == UNLIMITED):
+		_max_to_display = ABSOLUTE_MAX_DISPLAYED
+