fix(roaming): clock ticker moves the header time; GPS mirrors station pos

Two bugs from the last release:

1. The header clock was frozen: Date() was only evaluated during recomposition, and with no state changes the time never moved. Added a 1s LaunchedEffect ticker that updates a now-state, so the date/time text re-renders and actually advances — matching the reference app, which refreshes the clock on every location callback.

2. GPS indicator: replaced the 10-minute freshness check with a direct 'has a real fix' check (timestamp > 0 and coords non-zero). The page mirrors the station position (站位) from the shared StateFlow, so the GPS dot is green whenever the station has a fix — GPS shows exactly what the station GPS says, nothing more.

feature/roaming/src/main/java/com/rtbishop/look4sat/feature/roaming/RoamingScreen.kt

@@ -39,8 +39,11 @@ import androidx.compose.material3.Divider
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableLongStateOf
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
@@ -83,6 +86,16 @@ fun RoamingScreen() {
         RoamingState.fromPosition(stationPos)
     }
 
+    // Clock ticker: re-render date/time every second so the header clock
+    // actually moves (the reference app refreshes it on every location fix).
+    var now by remember { mutableLongStateOf(System.currentTimeMillis()) }
+    LaunchedEffect(Unit) {
+        while (true) {
+            now = System.currentTimeMillis()
+            kotlinx.coroutines.delay(1_000L)
+        }
+    }
+
     ScreenColumn(
         topBar = {
             TopBar { Text(text = "漫游", fontSize = 20.sp, fontWeight = FontWeight.Bold) }
@@ -93,14 +106,14 @@ fun RoamingScreen() {
             modifier = Modifier.fillMaxSize(),
             verticalArrangement = Arrangement.spacedBy(spacing.medium)
         ) {
-            InfoCard(state = state)
+            InfoCard(state = state, now = now)
             GridCard(state = state, modifier = Modifier.weight(1f))
         }
     }
 }
 
 @Composable
-private fun InfoCard(state: RoamingState) {
+private fun InfoCard(state: RoamingState, now: Long) {
     val colorScheme = MaterialTheme.colorScheme
     Column(
         modifier = Modifier
@@ -126,13 +139,13 @@ private fun InfoCard(state: RoamingState) {
             )
             Spacer(modifier = Modifier.weight(1f))
             Text(
-                text = SimpleDateFormat("dd MMM yyyy", Locale.getDefault()).format(Date()),
+                text = SimpleDateFormat("dd MMM yyyy", Locale.getDefault()).format(Date(now)),
                 fontSize = 14.sp,
                 color = colorScheme.onSecondaryContainer
             )
             Spacer(modifier = Modifier.width(12.dp))
             Text(
-                text = SimpleDateFormat("HH:mm", Locale.getDefault()).format(Date()),
+                text = SimpleDateFormat("HH:mm", Locale.getDefault()).format(Date(now)),
                 fontSize = 16.sp,
                 fontWeight = FontWeight.Medium,
                 color = colorScheme.onSecondaryContainer

feature/roaming/src/main/java/com/rtbishop/look4sat/feature/roaming/RoamingState.kt

@@ -44,7 +44,9 @@ data class RoamingState(
             val locator = positionToQth(pos.latitude, pos.longitude) ?: return RoamingState()
             val square = qthToSquare(locator)
             val squares = if (square != "----") qthNeighbors(square) else List(9) { "----" }
-            val fresh = pos.timestamp > 0L && System.currentTimeMillis() - pos.timestamp < 600_000L
+            // GPS is simply whatever the station position says — a real fix
+            // (non-zero, with timestamp) counts as enabled.
+            val hasFix = pos.timestamp > 0L && (pos.latitude != 0.0 || pos.longitude != 0.0)
             return RoamingState(
                 latitude = pos.latitude,
                 longitude = pos.longitude,
@@ -52,7 +54,7 @@ data class RoamingState(
                 gridSquares = squares,
                 markerX = markerFraction(locator, isLat = false),
                 markerY = markerFraction(locator, isLat = true),
-                gpsEnabled = fresh
+                gpsEnabled = hasFix
             )
         }