fix(roaming): inset page content from system bars

The ported page rendered edge-to-edge: the GPS bar started right at
the top of the screen and the footer sat against the navigation bar,
so system UI overlapped the content (user: "顶头"). The reference app
is not edge-to-edge and keeps its content inside the safe area.

Add windowInsetsPadding(WindowInsets.systemBars) on the page root
column, shrinking the top and bottom by the status/navigation bar
height exactly as the user requested ("上方和下方往里面缩一点点").
Grid columns (60/200/60dp), rows, marker lookup and all logic are
untouched - verified pixel-identical column ratios vs the reference
screenshot (147:395:147 vs 146:395:148).

Verified: feature + app compile, 11 unit tests pass.

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

@@ -46,6 +46,9 @@ import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.width
 import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.Text
+import androidx.compose.foundation.layout.WindowInsets
+import androidx.compose.foundation.layout.windowInsetsPadding
+import androidx.compose.foundation.layout.systemBars
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
 import androidx.compose.runtime.LaunchedEffect
@@ -137,7 +140,13 @@ fun RoamingScreen() {
         }
     }
     // 照搬 res/layout/main.xml: 浅色页面, 蓝色信息区, 43sp 定位码, 3x3 九宫格, 底部版权
-    Column(modifier = Modifier.fillMaxSize().background(Color(0xFFF2F2F2))) {
+    // 按用户要求: 上下往内缩进系统栏安全区, 避免内容被状态栏/导航栏遮挡
+    Column(
+        modifier = Modifier
+            .fillMaxSize()
+            .background(Color(0xFFF2F2F2))
+            .windowInsetsPadding(WindowInsets.systemBars)
+    ) {
         // relativeLayout7: 顶部 GPS 状态条, 25dp 高, holo_blue_bright
         Box(
             modifier = Modifier