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/build.gradle.kts

@@ -13,8 +13,8 @@ android {
         applicationId = "com.a2i.forwarder"
         minSdk = 34
         targetSdk = 36
-        versionCode = 22
+        versionCode = 23
-        versionName = "1.8.5"
+        versionName = "1.8.6"
     }
 
     signingConfigs {

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)
@@ -46,6 +68,11 @@ fun AppRoot() {
     val current = backStack?.destination?.route
     val showBar = current in tabRoutes
 
+    val app = A2iApp.instance
+    val updateInfo by app.updateChecker.updateInfo.collectAsState()
+    var showUpdateDialog by remember { mutableStateOf(false) }
+
+    Box {
         Scaffold(
             containerColor = MaterialTheme.colorScheme.background,
             bottomBar = {
@@ -96,4 +123,49 @@ fun AppRoot() {
                 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),
+        )
+    }
 }