feat: multi-server failover forwarding + reorder/enable

Bark servers now form an ordered failover chain: forwarding tries each
enabled server in list order, stopping at the first success.

- model: BarkServer.enabled (defaults true; legacy JSON compatible)
- core/BarkSender.pushToFirst: ordered try-until-success helper, shared
  by NotifyListenerService / PhoneCallMonitor / RetryWorker
- BarkClient.push uses msg.copy(deviceKey=server.deviceKey) so each
  server pushes its own key
- SettingsStore: drop currentServer/setCurrent; add moveServer +
  setServerEnabled; NotificationProcessor no longer sources deviceKey
- UI: ServerRow RadioButton -> Checkbox + per-row test/move-up/move-down;
  remove top "send test push" button; HomeScreen shows enabled count
- version 1.5.1 -> 1.6.0 (code 9 -> 10); CLAUDE.md synced

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

app/src/main/java/com/a2i/forwarder/service/NotifyListenerService.kt

@@ -3,7 +3,7 @@ package com.a2i.forwarder.service
 import android.service.notification.NotificationListenerService
 import android.service.notification.StatusBarNotification
 import com.a2i.forwarder.A2iApp
-import com.a2i.forwarder.core.BarkClient
+import com.a2i.forwarder.core.BarkSender
 import com.a2i.forwarder.core.ForwardLog
 import com.a2i.forwarder.core.NotificationProcessor
 import com.a2i.forwarder.core.PendingPush
@@ -58,20 +58,20 @@ class NotifyListenerService : NotificationListenerService() {
             return
         }
 
-        val server = app.settings.currentServer.value
-        if (server == null || server.deviceKey.isBlank()) {
-            app.logStore.addLog(ForwardLog(now, sbn.packageName, d.appLabel, msg.title, msg.body, "failed", "未配置 Bark key"))
+        val servers = app.settings.servers.value.filter { it.enabled && it.deviceKey.isNotBlank() }
+        if (servers.isEmpty()) {
+            app.logStore.addLog(ForwardLog(now, sbn.packageName, d.appLabel, msg.title, msg.body, "failed", "未配置可用 Bark 服务器"))
             return
         }
 
-        val result = BarkClient(server).push(msg)
+        val result = BarkSender.pushToFirst(servers, msg)
         if (result.isSuccess) {
             app.logStore.addLog(ForwardLog(now, sbn.packageName, d.appLabel, msg.title, msg.body, "sent", ""))
         } else {
             val reason = result.exceptionOrNull()?.message ?: "错误"
             app.logStore.addLog(ForwardLog(now, sbn.packageName, d.appLabel, msg.title, msg.body, "failed", reason))
             app.logStore.addPending(
-                PendingPush(UUID.randomUUID().toString(), now, server.id, json.encodeToString(msg))
+                PendingPush(UUID.randomUUID().toString(), now, servers.first().id, json.encodeToString(msg))
             )
         }
     }