fix: integration tests — sequential execution, IMAP timeouts, JMAP timeout

Root cause: flutter test ran all 3 integration test files in parallel
against the same Stalwart instance. Concurrent SMTP/IMAP from
email_repository_imap_test and concurrent_sync_test caused SMTP rate
limiting (4th send hung for ~27s) and flushPendingChanges race failures.

Fixes:
- stalwart-dev/test.sh: add --concurrency=1 so test files run serially
- concurrent_sync_test: reduce timeout 2 min → 30 s (tests now pass in ~2s)
- imap_client_factory + test helpers: set defaultResponseTimeout=20s on
  ImapClient so individual IMAP commands never block indefinitely
- jmap_client: reduce HTTP call timeout 30 s → 10 s (local server; keeps
  stacked-timeout total well below any reasonable per-test limit)

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

lib/data/imap/imap_client_factory.dart

@@ -21,7 +21,8 @@ Future<ImapClient> connectImap(
       'Unencrypted IMAP connections are not allowed. Enable SSL/TLS.',
     );
   }
-  final client = ImapClient();
+  final client =
+      ImapClient(defaultResponseTimeout: const Duration(seconds: 20));
   await client.connectToServer(account.imapHost, account.imapPort);
   await client.login(username, password);
   return client;

lib/data/jmap/jmap_client.dart

@@ -123,7 +123,7 @@ class JmapClient {
           },
           body: body,
         )
-        .timeout(const Duration(seconds: 30));
+        .timeout(const Duration(seconds: 10));
 
     if (resp.statusCode != 200) {
       throw JmapException('API call failed (HTTP ${resp.statusCode})');
@@ -160,7 +160,7 @@ class JmapClient {
           },
           body: data,
         )
-        .timeout(const Duration(seconds: 30));
+        .timeout(const Duration(seconds: 10));
     if (resp.statusCode != 200 && resp.statusCode != 201) {
       throw JmapException('Blob upload failed (HTTP ${resp.statusCode})');
     }

stalwart-dev/test.sh

@@ -62,6 +62,6 @@ export STALWART_IMAP_HOST="127.0.0.1"
 export STALWART_SMTP_HOST="127.0.0.1"
 
 START=$(date +%s)
-fvm flutter test test/integration/
+fvm flutter test --concurrency=1 test/integration/
 END=$(date +%s)
 echo "integration: $((END - START))s"

test/integration/concurrent_sync_test.dart

@@ -61,7 +61,9 @@ Future<enough_mail.ImapClient> _connectImapPlaintext(
   String username,
   String password,
 ) async {
-  final client = enough_mail.ImapClient();
+  final client = enough_mail.ImapClient(
+    defaultResponseTimeout: const Duration(seconds: 20),
+  );
   await client.connectToServer(
     account.imapHost,
     account.imapPort,
@@ -125,7 +127,7 @@ void main() {
   });
 
   test('concurrent IMAP + JMAP sync caches all emails without errors',
-      timeout: const Timeout(Duration(minutes: 2)), () async {
+      timeout: const Timeout(Duration(seconds: 30)), () async {
     final ts = DateTime.now().millisecondsSinceEpoch;
     const msgCount = 2;
 

test/integration/email_repository_imap_test.dart

@@ -27,7 +27,8 @@ Future<ImapClient> _imapConnect({
   required String user,
   required String pass,
 }) async {
-  final client = ImapClient();
+  final client =
+      ImapClient(defaultResponseTimeout: const Duration(seconds: 20));
   await client.connectToServer(host, port, isSecure: false);
   await client.login(user, pass);
   return client;
@@ -109,7 +110,8 @@ void main() {
     String username,
     String password,
   ) async {
-    final client = ImapClient();
+    final client =
+        ImapClient(defaultResponseTimeout: const Duration(seconds: 20));
     await client.connectToServer(a.imapHost, a.imapPort, isSecure: false);
     await client.login(username, password);
     return client;