feat: increase station coordinate precision to 5 decimals

Station lat/lon was stored rounded to 4 decimals (~11 m). Bump to 5 decimals (~1.1 m), slightly better than GPS hardware accuracy without showing noise.

- SettingsRepo.setStationPosition: round(4) -> round(5)
- QthConverter.qthToPosition: round(4) -> round(6) so 10-char locators fully roundtrip
- Update QthConverterTest expected values to 6-decimal precision

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/utility/QthConverter.kt

@@ -63,7 +63,7 @@ fun qthToPosition(locator: String): GeoPos? {
             latitude += 1.0 / 48.0
         }
     }
-    return GeoPos(latitude.round(4), longitude.round(4))
+    return GeoPos(latitude.round(6), longitude.round(6))
 }
 
 /**

core/domain/src/test/java/com/rtbishop/look4sat/core/domain/QthConverterTest.kt

@@ -26,14 +26,14 @@ class QthConverterTest {
     @Test
     fun `Given valid QTH returns correct POS`() {
         var result = qthToPosition("io91VL39FX")
-        assert(result?.latitude == 51.4999 && result.longitude == -0.2231)
+        assert(result?.latitude == 51.499913 && result.longitude == -0.22309)
         result = qthToPosition("gf15vc")
-        assert(result?.latitude == -34.8958 && result.longitude == -56.2083)
+        assert(result?.latitude == -34.895833 && result.longitude == -56.208333)
         // 8-char locators: finer 30" x 15" cell center
         result = qthToPosition("io91vl47")
-        assert(result?.latitude == 51.4896 && result.longitude == -0.2125)
+        assert(result?.latitude == 51.489583 && result.longitude == -0.2125)
         result = qthToPosition("jn58td25")
-        assert(result?.latitude == 48.1479 && result.longitude == 11.6042)
+        assert(result?.latitude == 48.147917 && result.longitude == 11.604167)
     }
 
     @Test