fix(android): prevent memory leaks from detached coroutine scopes

Critical fixes to prevent app crashes when screens are kept open for extended periods:

- Add repositoryScope with SupervisorJob for structured concurrency in TssRepository
- Replace detached CoroutineScope(Dispatchers.IO).launch with repositoryScope.launch:
  - Session event subscription (line 206)
  - Session status polling (line 291)
  - Message routing (line 1508)
- Add cleanup() method to properly cancel all jobs and repositoryScope
- Update disconnect() to also cancel sessionStatusPollingJob
- Update MainViewModel.onCleared() to call repository.cleanup()

This ensures all background coroutines are properly cancelled when the ViewModel
is cleared, preventing memory accumulation over time.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.claude/settings.local.json

@@ -553,7 +553,8 @@
       "Bash(\"/c/Users/dong/go/bin/go1.22.10.exe\" install golang.org/x/mobile/cmd/gobind@c31d5b91ecc32c0d598b8fe8457d244ca0b4e815)",
       "Bash(\"/c/Users/dong/go/bin/go1.22.10.exe\" mod tidy)",
       "Bash(adb devices:*)",
-      "Bash(adb logcat:*)"
+      "Bash(adb logcat:*)",
+      "Bash(git commit -m \"$\\(cat <<''EOF''\nfeat\\(android\\): add 5-minute polling timeout mechanism for keygen/sign\n\nImplements Electron''s checkAndTriggerKeygen\\(\\) polling fallback:\n- Adds polling every 2 seconds with 5-minute timeout\n- Triggers keygen/sign via synthetic session_started event on in_progress status\n- Handles gRPC stream disconnection when app goes to background\n- Shows timeout error in UI via existing error mechanism\n\n🤖 Generated with [Claude Code]\\(https://claude.com/claude-code\\)\n\nCo-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>\nEOF\n\\)\")"
     ],
     "deny": [],
     "ask": []

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

@@ -63,6 +63,10 @@ class TssRepository @Inject constructor(
     // Called when 5-minute polling timeout is reached without session starting
     private var keygenTimeoutCallback: ((String) -> Unit)? = null
 
+    // Repository-level CoroutineScope for background tasks
+    // Uses SupervisorJob so individual task failures don't cancel other tasks
+    private val repositoryScope = CoroutineScope(SupervisorJob() + Dispatchers.IO)
+
     companion object {
         // Polling interval for session status check (matching Electron's 2-second interval)
         private const val POLL_INTERVAL_MS = 2000L
@@ -142,6 +146,19 @@ class TssRepository @Inject constructor(
     fun disconnect() {
         messageCollectionJob?.cancel()
         sessionEventJob?.cancel()
+        sessionStatusPollingJob?.cancel()
+        grpcClient.disconnect()
+    }
+
+    /**
+     * Cleanup all resources when the repository is destroyed.
+     * Call this when the app is being destroyed to prevent memory leaks.
+     */
+    fun cleanup() {
+        messageCollectionJob?.cancel()
+        sessionEventJob?.cancel()
+        sessionStatusPollingJob?.cancel()
+        repositoryScope.cancel()
         grpcClient.disconnect()
     }
 
@@ -199,7 +216,7 @@ class TssRepository @Inject constructor(
     private fun startSessionEventSubscription() {
         sessionEventJob?.cancel()
         android.util.Log.d("TssRepository", "Starting session event subscription for partyId: $partyId")
-        sessionEventJob = CoroutineScope(Dispatchers.IO).launch {
+        sessionEventJob = repositoryScope.launch {
             grpcClient.subscribeSessionEvents(partyId).collect { event ->
                 android.util.Log.d("TssRepository", "=== Session event received ===")
                 android.util.Log.d("TssRepository", "  eventType: ${event.eventType}")
@@ -284,7 +301,7 @@ class TssRepository @Inject constructor(
 
         android.util.Log.d("TssRepository", "[POLLING] Starting session status polling for $sessionType session: $sessionId")
 
-        sessionStatusPollingJob = CoroutineScope(Dispatchers.IO).launch {
+        sessionStatusPollingJob = repositoryScope.launch {
             val startTime = System.currentTimeMillis()
             var pollCount = 0
 
@@ -1501,7 +1518,7 @@ class TssRepository @Inject constructor(
         currentMessageRoutingPartyIndex = partyIndex
 
         messageCollectionJob?.cancel()
-        messageCollectionJob = CoroutineScope(Dispatchers.IO).launch {
+        messageCollectionJob = repositoryScope.launch {
             // Collect outgoing messages from TSS and route via gRPC
             launch {
                 tssNativeBridge.outgoingMessages.collect { message ->

backend/mpc-system/services/service-party-android/app/src/main/java/com/durian/tssparty/presentation/viewmodel/MainViewModel.kt

@@ -1204,7 +1204,7 @@ class MainViewModel @Inject constructor(
 
     override fun onCleared() {
         super.onCleared()
-        repository.disconnect()
+        repository.cleanup()
     }
 }