fix(android): 修复重连时gRPC流异常导致待机闪退

问题：心跳失败触发重连时，shutdownNow关闭旧channel会导致
gRPC流抛出UNAVAILABLE异常，虽然检测到过时流但仍传播异常
到TssRepository的collect协程，导致应用崩溃。

修复：
- GrpcClient: 过时流错误时使用close()而非close(t)避免传播异常
- GrpcClient: 添加shutdownNow错误检测避免不必要的重连
- TssRepository: 为subscribeSessionEvents和subscribeMessages流添加.catch

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/mpc-system/services/service-party-android/app/src/main/java/com/durian/tssparty/data/remote/GrpcClient.kt

@@ -790,15 +790,16 @@ class GrpcClient @Inject constructor() {
             override fun onError(t: Throwable) {
                 Log.e(TAG, "Message stream error: ${t.message}")
 
-                // Ignore events from stale streams
+                // Ignore events from stale streams - close without exception to avoid crash
                 if (messageStreamVersion.get() != streamVersion) {
                     Log.d(TAG, "Ignoring error from stale message stream")
-                    close(t)
+                    close()
                     return
                 }
 
-                // Don't trigger reconnect for CANCELLED errors
+                // Don't trigger reconnect for CANCELLED or channel shutdown errors
-                if (!t.message.orEmpty().contains("CANCELLED")) {
+                val errorMessage = t.message.orEmpty()
+                if (!errorMessage.contains("CANCELLED") && !errorMessage.contains("shutdownNow")) {
                     triggerReconnect("Message stream error: ${t.message}")
                 }
                 close(t)
@@ -870,15 +871,16 @@ class GrpcClient @Inject constructor() {
             override fun onError(t: Throwable) {
                 Log.e(TAG, "Session event stream error: ${t.message}")
 
-                // Ignore events from stale streams
+                // Ignore events from stale streams - close without exception to avoid crash
                 if (eventStreamVersion.get() != streamVersion) {
                     Log.d(TAG, "Ignoring error from stale event stream")
-                    close(t)
+                    close()
                     return
                 }
 
-                // Don't trigger reconnect for CANCELLED errors
+                // Don't trigger reconnect for CANCELLED or channel shutdown errors
-                if (!t.message.orEmpty().contains("CANCELLED")) {
+                val errorMessage = t.message.orEmpty()
+                if (!errorMessage.contains("CANCELLED") && !errorMessage.contains("shutdownNow")) {
                     triggerReconnect("Event stream error: ${t.message}")
                 }
                 close(t)

backend/mpc-system/services/service-party-android/app/src/main/java/com/durian/tssparty/data/repository/TssRepository.kt

@@ -284,7 +284,12 @@ class TssRepository @Inject constructor(
         currentSessionEventPartyId = effectivePartyId
         android.util.Log.d("TssRepository", "Starting session event subscription for partyId: $effectivePartyId (device partyId: $partyId)")
         sessionEventJob = repositoryScope.launch {
-            grpcClient.subscribeSessionEvents(effectivePartyId).collect { event ->
+            grpcClient.subscribeSessionEvents(effectivePartyId)
+                .catch { e ->
+                    // Log error but don't crash - connection will be restored by GrpcClient
+                    android.util.Log.e("TssRepository", "Session event stream error: ${e.message}")
+                }
+                .collect { event ->
                 android.util.Log.d("TssRepository", "=== Session event received ===")
                 android.util.Log.d("TssRepository", "  eventType: ${event.eventType}")
                 android.util.Log.d("TssRepository", "  sessionId: ${event.sessionId}")
@@ -1859,7 +1864,12 @@ class TssRepository @Inject constructor(
 
             // Collect incoming messages from gRPC and send to TSS
             launch {
-                grpcClient.subscribeMessages(sessionId, effectivePartyId).collect { message ->
+                grpcClient.subscribeMessages(sessionId, effectivePartyId)
+                    .catch { e ->
+                        // Log error but don't crash - connection will be restored by GrpcClient
+                        android.util.Log.e("TssRepository", "Message stream error: ${e.message}")
+                    }
+                    .collect { message ->
                     // Find party index from party ID
                     val session = _currentSession.value
                     val fromPartyIndex = session?.participants?.find { it.partyId == message.fromParty }?.partyIndex