feat: Improve bottom navigation bar accessibility and add auto-hide feature

- Improve the accessibility of the bottom navigation bar by adding semantics for tab roles, selection status, and content descriptions.
- Add an auto-hide feature to the bottom navigation bar, triggered by accessibility touch events.
- Refactor bottom navigation bar `alwaysShowLabel` property.

Author: jing332

app/src/main/java/com/github/jing332/tts_server_android/compose/MainPager.kt

@@ -31,7 +31,14 @@ import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.input.nestedscroll.nestedScroll
+import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.semantics.Role
+import androidx.compose.ui.semantics.clearAndSetSemantics
+import androidx.compose.ui.semantics.contentDescription
+import androidx.compose.ui.semantics.role
+import androidx.compose.ui.semantics.selected
+import com.github.jing332.compose.widgets.ControlBottomBarVisibility
 import com.github.jing332.compose.widgets.rememberA11TouchEnabled
 import com.github.jing332.tts_server_android.compose.forwarder.systts.SystemTtsForwarderScreen
 import com.github.jing332.tts_server_android.compose.settings.SettingsScreen
@@ -62,13 +69,15 @@ fun AnimatedContentScope.MainPager(sharedVM: SharedViewModel) {
         }
     }
 
+    val context = LocalContext.current
     val scope = rememberCoroutineScope()
     MigrationTips()
 
     val a11yTouchEnabled = rememberA11TouchEnabled()
     val scrollBehavior = BottomAppBarDefaults.exitAlwaysScrollBehavior(canScroll = {
         !a11yTouchEnabled
     })
+    ControlBottomBarVisibility(a11yTouchEnabled, scrollBehavior)
 
     val overlayController = rememberOverlayController()
 
@@ -115,8 +124,13 @@ fun AnimatedContentScope.MainPager(sharedVM: SharedViewModel) {
                             for (destination in PagerDestination.routes) {
                                 val isSelected = pagerState.currentPage == destination.index
                                 NavigationBarItem(
+                                    modifier = Modifier.clearAndSetSemantics {
+                                        role = Role.Tab
+                                        selected = isSelected
+                                        contentDescription = context.getString(destination.strId)
+                                    },
                                     selected = isSelected,
-                                    alwaysShowLabel = a11yTouchEnabled,
+                                    alwaysShowLabel = false,
                                     onClick = {
                                         scope.launch {
                                             pagerState.animateScrollToPage(destination.index)

lib-compose/src/main/java/com/github/jing332/compose/widgets/ControlBottomBarVisibility.kt

@@ -10,6 +10,36 @@ import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.remember
 
 
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun ControlBottomBarVisibility(
+    state: Boolean,
+    bottomBarBehavior: BottomAppBarScrollBehavior,
+) {
+    val bottomAppBarState = bottomBarBehavior.state
+
+    val heightOffset =
+        remember { androidx.compose.animation.core.Animatable(1f) }
+
+    LaunchedEffect(heightOffset.value) {
+        bottomAppBarState.heightOffset = heightOffset.value
+    }
+
+    LaunchedEffect(state) {
+        if (state) {
+            heightOffset.snapTo(bottomAppBarState.heightOffset)
+            heightOffset.animateTo(
+                targetValue = 0f,
+                animationSpec = tween(
+                    durationMillis = 300,
+                    easing = FastOutSlowInEasing
+                )
+            )
+        }
+    }
+
+}
+
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
 fun ControlBottomBarVisibility(