New Portable

Ensure alliance/horde learning counters match MAX_BUTTONS and migrate old saved data to avoid nil arithmetic errors. Updated default counters to include 18 entries, added a defensive migration in ADDON_LOADED that pads saved allianceCounter/hordeCounter to MAX_BUTTONS (or 18) because AceDB does not extend array parts, and made the click increment nil-safe ((c[id] or 0) + 1). Also bumped addon version to 20.1. This prevents errors when clicking the highest-numbered button after upgrading from older versions.