Objects and items now display with their own names on the map instead of
the originating station's callsign. This prevents confusion where stations
creating objects (like repeaters) appear at multiple locations.
For example, CALGRY creates repeater objects (147.06-WC, 146.85-NH) which
were appearing on the map labeled as "CALGRY" at the repeater locations
instead of showing the actual object names.
Changes:
- Updated map_label() to return object_name for object packets
- Updated map_label() to return item_name for item packets
- Position packets continue to show the sender callsign
- Updated tests to expect object/item names instead of sender
This matches APRS.fi behavior where objects are displayed separately
from their originating station.