fix: 修正即時聊天室 presence channel 間歇性失效

三個根本原因：
1. updateEchoToken() 呼叫 disconnect/connect 會中斷已訂閱的
   presence channel，改為只更新 auth header（不重連）。
   同時將 setAuth() 的呼叫順序改為先 updateEchoToken() 再
   startRealtime()，確保訂閱時使用最新 token。
2. BookingPresenceChannel::join() 未對 schedule null 做防守，
   載入後若 schedule 不存在會 500，導致 auth 靜默失敗。
3. WebSocket 重連後 presence channel 不會自動恢復，
   在 BookingChat 加入 reconnected 事件處理，重連後重訂閱。

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/Broadcasting/BookingPresenceChannel.php

@@ -16,7 +16,9 @@ class BookingPresenceChannel
         $booking->loadMissing('schedule');
 
         $isMember = $user->role === 'member' && $booking->member_id === $user->id;
-        $isProvider = $user->role === 'provider' && $booking->schedule->provider_id === $user->id;
+        $isProvider = $user->role === 'provider'
+            && $booking->schedule !== null
+            && $booking->schedule->provider_id === $user->id;
 
         if (!$isMember && !$isProvider) {
             return false;

frontend/src/components/BookingChat.vue

@@ -170,15 +170,24 @@ function subscribeChannel() {
     })
 }
 
+function handleReconnected() {
+  if (!isConfirmed.value) return
+  echo.leave(`booking.${props.bookingId}`)
+  channel.value = null
+  subscribeChannel()
+}
+
 onMounted(async () => {
   await requestBrowserNotificationPermission()
   await loadHistory()
   if (isConfirmed.value) {
     subscribeChannel()
+    echo.connector.pusher.connection.bind('reconnected', handleReconnected)
   }
 })
 
 onUnmounted(() => {
+  echo.connector.pusher.connection.unbind('reconnected', handleReconnected)
   if (channel.value) {
     channel.value.whisper('presence', { user_type: props.currentUserType, online: false })
     echo.leave(`booking.${props.bookingId}`)

frontend/src/plugins/echo.js

@@ -27,10 +27,13 @@ const echo = new Echo({
 // 登入後更新 auth header，讓 presence channel 授權帶正確 token
 export function updateEchoToken() {
     const token = getAuthToken()
-    echo.options.auth.headers.Authorization = `Bearer ${token}`
-    // 重新連線讓新 token 生效
-    echo.disconnect()
-    echo.connect()
+    const bearer = `Bearer ${token}`
+    echo.options.auth.headers.Authorization = bearer
+    // 同步更新 Pusher 內部 config（避免 Pusher.js 持有舊的 header copy）
+    if (echo.connector?.pusher?.config?.auth?.headers) {
+        echo.connector.pusher.config.auth.headers.Authorization = bearer
+    }
+    // 不 disconnect/connect：避免中斷 BookingChat 已訂閱的 presence channel
 }
 
 export default echo

frontend/src/stores/auth.js

@@ -29,8 +29,8 @@ export const useAuthStore = defineStore('auth', () => {
     localStorage.setItem('user', JSON.stringify(userData))
     const ns = useNotificationStore()
     ns.startPolling()
-    ns.startRealtime(userData.id)
     updateEchoToken()
+    ns.startRealtime(userData.id)
   }
 
   async function logout() {

frontend/src/stores/coachAuth.js

@@ -29,8 +29,8 @@ export const useCoachAuthStore = defineStore('coachAuth', () => {
     localStorage.setItem('coach_user', JSON.stringify(userData))
     const ns = useNotificationStore()
     ns.startPolling()
-    ns.startRealtime(userData.id)
     updateEchoToken()
+    ns.startRealtime(userData.id)
   }
 
   async function logout() {