Add displayField configuration to award definitions

Add configurable displayField to award definitions to control what
is shown in award details instead of always using the entity value.

## Award Definitions Updated
- DXCC: displayField = 'entity' (shows country name)
- DXCC CW: displayField = 'entity' (shows country name)
- WAS: displayField = 'state' (shows state name)
- VUCC: displayField = 'grid' (shows grid square)
- RS-44: displayField = 'callsign' (shows callsign)

## Backend Changes
- Preserve displayField when normalizing award rules
- Use displayField to determine entity name in details
- Fallback logic for awards without displayField
- Add satName to entity data for better display

This fixes VUCC showing grid squares instead of country names.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

award-definitions/vucc-sat.json

@@ -7,6 +7,7 @@
     "type": "entity",
     "entityType": "grid",
     "target": 100,
+    "displayField": "grid",
     "filters": {
       "operator": "AND",
       "filters": [