fix: устранение race condition и улучшение диагностики синхронизации

- SyncPricelists() теперь захватывает pricelistMu, предотвращая параллельный
  запуск фонового тикера и ручного sync (было причиной UNIQUE constraint ошибки)
- Дедупликация lot_name в fetchServerPricelistItems на случай дублей на сервере
- PushPendingChanges пишет запись в sync_log (тип "changes") при каждом запуске
- syncPricelists вызывает reportClientSchemaState через defer — состояние
  клиента отправляется на сервер независимо от исхода синхронизации

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

internal/services/sync/service.go

@@ -322,6 +322,12 @@ func (s *Service) NeedSync() (bool, error) {
 
 // SyncPricelists synchronizes all active pricelists from server to local SQLite
 func (s *Service) SyncPricelists() (int, error) {
+	s.pricelistMu.Lock()
+	defer s.pricelistMu.Unlock()
+	return s.syncPricelists()
+}
+
+func (s *Service) syncPricelists() (int, error) {
 	slog.Info("starting pricelist sync")
 	plSyncStart := time.Now()
 	if _, err := s.EnsureReadinessForSync(); err != nil {
@@ -336,6 +342,12 @@ func (s *Service) SyncPricelists() (int, error) {
 		return 0, fmt.Errorf("database not available: %w", err)
 	}
 
+	defer func() {
+		if reportErr := s.reportClientSchemaState(mariaDB, time.Now().UTC()); reportErr != nil {
+			slog.Warn("failed to report client state after pricelist sync", "error", reportErr)
+		}
+	}()
+
 	// Create repository
 	pricelistRepo := repository.NewPricelistRepository(mariaDB)
 
@@ -764,9 +776,16 @@ func (s *Service) fetchServerPricelistItems(serverPricelistID uint) ([]localdb.L
 		return nil, fmt.Errorf("getting server pricelist items: %w", err)
 	}
 
-	localItems := make([]localdb.LocalPricelistItem, len(serverItems))
-	for i, item := range serverItems {
-		localItems[i] = *localdb.PricelistItemToLocal(&item, 0)
+	seen := make(map[string]struct{}, len(serverItems))
+	localItems := make([]localdb.LocalPricelistItem, 0, len(serverItems))
+	for i := range serverItems {
+		lotName := serverItems[i].LotName
+		if _, dup := seen[lotName]; dup {
+			slog.Warn("duplicate lot_name in server pricelist, skipping", "pricelist_id", serverPricelistID, "lot_name", lotName)
+			continue
+		}
+		seen[lotName] = struct{}{}
+		localItems = append(localItems, *localdb.PricelistItemToLocal(&serverItems[i], 0))
 	}
 
 	return localItems, nil
@@ -843,7 +862,7 @@ func (s *Service) SyncPricelistsIfNeeded() error {
 	}
 
 	slog.Info("new pricelists detected, syncing...")
-	_, err = s.SyncPricelists()
+	_, err = s.syncPricelists()
 	if err != nil {
 		return fmt.Errorf("syncing pricelists: %w", err)
 	}
@@ -888,7 +907,10 @@ func (s *Service) PushPendingChanges() (int, error) {
 	}
 
 	slog.Info("pushing pending changes", "count", len(changes))
+	pushStart := time.Now()
 	pushed := 0
+	failed := 0
+	var firstErr string
 	var syncedIDs []int64
 	sortedChanges := prioritizeProjectChanges(changes)
 
@@ -899,6 +921,10 @@ func (s *Service) PushPendingChanges() (int, error) {
 			slog.Warn("failed to push change", "id", change.ID, "type", change.EntityType, "operation", change.Operation, "error", err)
 			newAttempts := change.Attempts + 1
 			s.localDB.IncrementPendingChangeAttempts(change.ID, err.Error())
+			if firstErr == "" {
+				firstErr = err.Error()
+			}
+			failed++
 			if newAttempts >= maxPendingChangeAttempts {
 				slog.Error("abandoning pending change after max attempts",
 					"id", change.ID, "type", change.EntityType, "op", change.Operation,
@@ -919,7 +945,13 @@ func (s *Service) PushPendingChanges() (int, error) {
 		}
 	}
 
-	slog.Info("pending changes pushed", "pushed", pushed, "failed", len(changes)-pushed)
+	if failed > 0 {
+		s.localDB.AppendSyncLog("changes", "error", firstErr, pushed, pushStart, time.Since(pushStart).Milliseconds())
+	} else {
+		s.localDB.AppendSyncLog("changes", "ok", "", pushed, pushStart, time.Since(pushStart).Milliseconds())
+	}
+
+	slog.Info("pending changes pushed", "pushed", pushed, "failed", failed)
 	return pushed, nil
 }