Add optional individual MWL port icon discovery

[jneb802]

Summary

• add synced config Port Icons Individual, default Off
• when Off, ports keep the existing vanilla shared IconPlaced map icon behavior
• when On, ports stop using vanilla IconPlaced icons and instead discover/save map icons per player when the player gets close to a port
• keep port travel unlocks tied to interaction via the existing MWL_KnownPorts field
• store individual icon discoveries in the existing character custom data field MWL_KnownPortIcons

Data behavior

• Existing MWL_KnownPorts data is preserved and remains unchanged
• Existing vanilla shared port icons remain the default because the new config defaults Off
• The individual icon system intentionally does not manage icons per world

Testing

• dotnet build /Users/benjmarston/Develop/MoreWorldLocations_All/MoreWorldLocations_All.sln