v4.1.1: Input zone fixes, MQTT postfix and Robot sprite

New features

• Robot scroll sprite: Added an original 8×8 Robot with blinking eyes, replacing Mario in the IN and OUT scroll effects. Updated the effect selector and README to use ROBOT.
• Automatic migration: Existing settings, profiles and restored backups using MARIO automatically use ROBOT. The legacy MARIO identifier remains accepted through MQTT and the API.

Fixes

• Stale text in Manual/MQTT zones: With Disable service messages enabled, Manual input and MQTT client zones now start empty after a restart, profile application or mode change. Text from the previous mode, earlier input and startup test messages is cleared while the zone waits for new input.
• Clearing MQTT postfixes: Clearing a zone's MQTT postfix field now saves an empty value instead of keeping the previous suffix. This works in both the default and additional profiles, with Save and Apply Now.
• Changing sprites through MQTT: Fixed sprite updates when changing scroll effects through MQTT, so the selected sprite takes effect correctly.