feat: extend sync log with skipped count and bytes transferred

Track how many emails were already up-to-date (skipped) and the
approximate bytes transferred per sync cycle. SyncEmailsResult
accumulates fetched/skipped/bytes across mailboxes; DB schema v11
adds emailsSkipped and bytesTransferred columns to sync_logs.
SyncLogScreen shows "X new · Y up-to-date · took Zs" in the tile
subtitle with full detail rows in the expansion panel.

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

test/integration/account_sync_manager_test.dart

@@ -71,7 +71,8 @@ class _FakeEmails implements EmailRepository {
       const EmailBody(emailId: '', attachments: []);
 
   @override
-  Future<int> syncEmails(String a, String m) async => 0;
+  Future<SyncEmailsResult> syncEmails(String a, String m) async =>
+      SyncEmailsResult.zero;
 
   @override
   Future<void> setFlag(String id, {bool? seen, bool? flagged}) async {}

test/unit/account_sync_manager_test.dart

@@ -71,7 +71,11 @@ class FakeEmailRepository implements EmailRepository {
       const EmailBody(emailId: '', attachments: []);
 
   @override
-  Future<int> syncEmails(String accountId, String mailboxPath) async => 0;
+  Future<SyncEmailsResult> syncEmails(
+    String accountId,
+    String mailboxPath,
+  ) async =>
+      SyncEmailsResult.zero;
 
   @override
   Future<void> setFlag(String emailId, {bool? seen, bool? flagged}) async {}
@@ -157,9 +161,12 @@ class _CountingEmailRepository extends FakeEmailRepository {
   final List<String> syncedPaths = [];
 
   @override
-  Future<int> syncEmails(String accountId, String mailboxPath) async {
+  Future<SyncEmailsResult> syncEmails(
+    String accountId,
+    String mailboxPath,
+  ) async {
     syncedPaths.add(mailboxPath);
-    return 0;
+    return SyncEmailsResult.zero;
   }
 }
 
@@ -167,10 +174,13 @@ class FailingJmapEmailRepository extends FakeEmailRepository {
   int syncCount = 0;
 
   @override
-  Future<int> syncEmails(String accountId, String mailboxPath) async {
+  Future<SyncEmailsResult> syncEmails(
+    String accountId,
+    String mailboxPath,
+  ) async {
     syncCount++;
     if (syncCount == 1) throw Exception('simulated JMAP failure');
-    return 0;
+    return SyncEmailsResult.zero;
   }
 }
 

test/unit/sync_log_repository_impl_test.dart

@@ -37,8 +37,10 @@ void main() {
       success: true,
       protocol: 'imap',
       emailsFetched: 5,
+      emailsSkipped: 0,
       mailboxesSynced: 3,
       pendingFlushed: 0,
+      bytesTransferred: 0,
       startedAt: start,
       finishedAt: end,
     );
@@ -65,8 +67,10 @@ void main() {
       errorMessage: 'Connection refused',
       protocol: 'imap',
       emailsFetched: 0,
+      emailsSkipped: 0,
       mailboxesSynced: 0,
       pendingFlushed: 0,
+      bytesTransferred: 0,
       startedAt: start,
       finishedAt: end,
     );

test/widget/helpers.dart

@@ -156,7 +156,11 @@ class FakeEmailRepository implements EmailRepository {
   Future<EmailBody> getEmailBody(String emailId) async => _emailBody;
 
   @override
-  Future<int> syncEmails(String accountId, String mailboxPath) async => 0;
+  Future<SyncEmailsResult> syncEmails(
+    String accountId,
+    String mailboxPath,
+  ) async =>
+      SyncEmailsResult.zero;
 
   @override
   Future<void> setFlag(String emailId, {bool? seen, bool? flagged}) async {}