Enhance aircraft details display to match dump1090 format

- Add country lookup from ICAO hex codes with flag display
- Implement UTC clocks and last update time indicators
- Enhance aircraft table with ICAO, squawk, and RSSI columns
- Add color-coded RSSI signal strength indicators
- Fix calculateDistance returning string instead of number
- Accept all SBS-1 message types for complete data capture
- Improve data merging to preserve country and registration

🤖 Generated with [Claude Code](https://claude.ai/code)

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

internal/client/dump1090.go

@@ -136,6 +136,14 @@ func (c *Dump1090Client) updateExistingAircraft(existing, update *parser.Aircraf
 		existing.Squawk = update.Squawk
 	}
 	existing.OnGround = update.OnGround
+	
+	// Preserve country and registration
+	if update.Country != "" && update.Country != "Unknown" {
+		existing.Country = update.Country
+	}
+	if update.Registration != "" {
+		existing.Registration = update.Registration
+	}
 }
 
 func (c *Dump1090Client) shouldAddTrackPoint(existing, update *parser.Aircraft) bool {