feat: floating update badge across all pages

Small pulsing circle icon (top-right) that persists across all tabs,
blinks slowly (alpha 0.35↔1.0, 1.2s cycle). Tapping opens UpdateDialog.

version 1.8.5 -> 1.8.6 (code 22 -> 23)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src/main/java/com/a2i/forwarder/ui/nav/AppNav.kt

@@ -1,7 +1,20 @@
 package com.a2i.forwarder.ui.nav
 
+import androidx.compose.animation.core.RepeatMode
+import androidx.compose.animation.core.animateFloat
+import androidx.compose.animation.core.infiniteRepeatable
+import androidx.compose.animation.core.rememberInfiniteTransition
+import androidx.compose.animation.core.tween
+import androidx.compose.foundation.background
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.SystemUpdate
 import androidx.compose.material.icons.outlined.Apps
 import androidx.compose.material.icons.outlined.FilterAlt
 import androidx.compose.material.icons.outlined.Notifications
@@ -14,8 +27,15 @@ import androidx.compose.material3.NavigationBarItemDefaults
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+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.alpha
+import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.vector.ImageVector
 import androidx.compose.ui.unit.dp
 import androidx.navigation.NavGraph.Companion.findStartDestination
@@ -23,11 +43,13 @@ import androidx.navigation.compose.NavHost
 import androidx.navigation.compose.composable
 import androidx.navigation.compose.currentBackStackEntryAsState
 import androidx.navigation.compose.rememberNavController
+import com.a2i.forwarder.A2iApp
 import com.a2i.forwarder.ui.screens.AppManageScreen
 import com.a2i.forwarder.ui.screens.FilterScreen
 import com.a2i.forwarder.ui.screens.HomeScreen
 import com.a2i.forwarder.ui.screens.LogScreen
 import com.a2i.forwarder.ui.screens.SettingsScreen
+import com.a2i.forwarder.ui.screens.UpdateDialog
 
 private sealed class Tab(val route: String, val label: String, val icon: ImageVector) {
     object Home : Tab("home", "首页", Icons.Outlined.Notifications)
@@ -46,54 +68,104 @@ fun AppRoot() {
     val current = backStack?.destination?.route
     val showBar = current in tabRoutes
 
-    Scaffold(
-        containerColor = MaterialTheme.colorScheme.background,
-        bottomBar = {
-            if (showBar) {
-                NavigationBar(
-                    containerColor = MaterialTheme.colorScheme.surface,
-                    tonalElevation = 0.dp,
-                ) {
-                    tabs.forEach { t ->
-                        NavigationBarItem(
-                            selected = current == t.route,
-                            onClick = {
-                                nav.navigate(t.route) {
-                                    popUpTo(nav.graph.findStartDestination().id) { saveState = true }
-                                    launchSingleTop = true
-                                    restoreState = true
-                                }
-                            },
-                            icon = { Icon(t.icon, t.label) },
-                            label = { Text(t.label) },
-                            colors = NavigationBarItemDefaults.colors(
-                                selectedIconColor = MaterialTheme.colorScheme.primary,
-                                selectedTextColor = MaterialTheme.colorScheme.primary,
-                                indicatorColor = MaterialTheme.colorScheme.primaryContainer,
-                                unselectedIconColor = MaterialTheme.colorScheme.onSurfaceVariant,
-                                unselectedTextColor = MaterialTheme.colorScheme.onSurfaceVariant,
-                            ),
-                        )
+    val app = A2iApp.instance
+    val updateInfo by app.updateChecker.updateInfo.collectAsState()
+    var showUpdateDialog by remember { mutableStateOf(false) }
+
+    Box {
+        Scaffold(
+            containerColor = MaterialTheme.colorScheme.background,
+            bottomBar = {
+                if (showBar) {
+                    NavigationBar(
+                        containerColor = MaterialTheme.colorScheme.surface,
+                        tonalElevation = 0.dp,
+                    ) {
+                        tabs.forEach { t ->
+                            NavigationBarItem(
+                                selected = current == t.route,
+                                onClick = {
+                                    nav.navigate(t.route) {
+                                        popUpTo(nav.graph.findStartDestination().id) { saveState = true }
+                                        launchSingleTop = true
+                                        restoreState = true
+                                    }
+                                },
+                                icon = { Icon(t.icon, t.label) },
+                                label = { Text(t.label) },
+                                colors = NavigationBarItemDefaults.colors(
+                                    selectedIconColor = MaterialTheme.colorScheme.primary,
+                                    selectedTextColor = MaterialTheme.colorScheme.primary,
+                                    indicatorColor = MaterialTheme.colorScheme.primaryContainer,
+                                    unselectedIconColor = MaterialTheme.colorScheme.onSurfaceVariant,
+                                    unselectedTextColor = MaterialTheme.colorScheme.onSurfaceVariant,
+                                ),
+                            )
+                        }
                     }
                 }
+            },
+        ) { inner ->
+            NavHost(
+                navController = nav,
+                startDestination = Tab.Home.route,
+                modifier = Modifier.padding(inner),
+            ) {
+                composable(Tab.Home.route) {
+                    HomeScreen(
+                        onOpenLog = { nav.navigate("log") },
+                        onOpenSettings = { nav.navigate(Tab.Settings.route) },
+                    )
+                }
+                composable(Tab.Apps.route) { AppManageScreen() }
+                composable(Tab.Filter.route) { FilterScreen() }
+                composable(Tab.Settings.route) { SettingsScreen(onOpenLog = { nav.navigate("log") }) }
+                composable("log") { LogScreen(onBack = { nav.popBackStack() }) }
             }
-        },
-    ) { inner ->
-        NavHost(
-            navController = nav,
-            startDestination = Tab.Home.route,
-            modifier = Modifier.padding(inner),
-        ) {
-            composable(Tab.Home.route) {
-                HomeScreen(
-                    onOpenLog = { nav.navigate("log") },
-                    onOpenSettings = { nav.navigate(Tab.Settings.route) },
-                )
-            }
-            composable(Tab.Apps.route) { AppManageScreen() }
-            composable(Tab.Filter.route) { FilterScreen() }
-            composable(Tab.Settings.route) { SettingsScreen(onOpenLog = { nav.navigate("log") }) }
-            composable("log") { LogScreen(onBack = { nav.popBackStack() }) }
+        }
+
+        // 浮动更新提醒小图标（跨所有页面，缓慢闪烁）
+        if (updateInfo != null) {
+            UpdateBadge(
+                modifier = Modifier.align(Alignment.TopEnd),
+                onClick = { showUpdateDialog = true },
+            )
         }
     }
+
+    if (showUpdateDialog && updateInfo != null) {
+        UpdateDialog(updateInfo!!, onDismiss = { showUpdateDialog = false })
+    }
+}
+
+/** 跨页面浮动更新提醒：右上角小圆点 + 缓慢闪烁动画。 */
+@Composable
+private fun UpdateBadge(modifier: Modifier = Modifier, onClick: () -> Unit) {
+    val transition = rememberInfiniteTransition(label = "updateBlink")
+    val pulseAlpha by transition.animateFloat(
+        initialValue = 0.35f,
+        targetValue = 1f,
+        animationSpec = infiniteRepeatable(
+            animation = tween(1200),
+            repeatMode = RepeatMode.Reverse,
+        ),
+        label = "pulseAlpha",
+    )
+
+    Box(
+        modifier = modifier
+            .padding(top = 12.dp, end = 12.dp)
+            .size(40.dp)
+            .alpha(pulseAlpha)
+            .background(MaterialTheme.colorScheme.primary, CircleShape)
+            .clickable(onClick = onClick),
+        contentAlignment = Alignment.Center,
+    ) {
+        Icon(
+            Icons.Filled.SystemUpdate,
+            contentDescription = "发现新版本，点击更新",
+            tint = Color.White,
+            modifier = Modifier.size(22.dp),
+        )
+    }
 }