feat(map): first-call callsign label toggle in VUCC grid mode

Add a 'first call' pill toggle below the grid-mode switch (map top-right,
visible only in grid mode + VUCC award). When on, worked (green) cells are
labelled with the first callsign worked in that grid (earliest confirmed
QSO by time) instead of the Maidenhead code; non-worked cells get no label
at all. Persisted via OtherSettings.stateOfMapFirstCall (full MVI chain).
The feature is VUCC-only: All and other award overlays never draw it.

core/presentation/src/main/res/values-zh/strings.xml

@@ -109,6 +109,7 @@
     <string name="map_next">下一个</string>
     <string name="map_grid_mode">网格模式</string>
     <string name="map_satellite_mode">卫星模式</string>
+    <string name="map_first_call_mode">首通呼号</string>
     <string name="map_azimuth">方位角：%.1f°</string>
     <string name="map_elevation">仰角：%.1f°</string>
     <string name="map_altitude">高度：%.0f km</string>

core/presentation/src/main/res/values/strings.xml

@@ -133,6 +133,7 @@
     <string name="map_copyright" translatable="false">© OpenStreetMap contributors</string>
     <string name="map_grid_mode">Grid mode</string>
     <string name="map_satellite_mode">Satellite mode</string>
+    <string name="map_first_call_mode">First call</string>
     <string name="map_azimuth">Azimuth: %.1f°</string>
     <string name="map_elevation">Elevation: %.1f°</string>
     <string name="map_altitude">Altitude: %.0f km</string>