fix: display only real sync errors in error count and list

- Added CountErroredChanges() method to count only pending changes with LastError
- Previously, error count included all pending changes, not just failed ones
- Added /api/sync/info endpoint with proper error count and error list
- Added sync info modal to display sync status, error count, and error details
- Made sync status indicators clickable to open the modal
- Fixed disconnect between "Error count: 4" and "No errors" in the list

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

internal/handlers/sync.go

@@ -282,6 +282,70 @@ func (h *SyncHandler) GetPendingChanges(c *gin.Context) {
 	})
 }
 
+// SyncInfoResponse represents sync information
+type SyncInfoResponse struct {
+	LastSyncAt *time.Time `json:"last_sync_at"`
+	IsOnline   bool       `json:"is_online"`
+	ErrorCount int        `json:"error_count"`
+	Errors     []SyncError `json:"errors,omitempty"`
+}
+
+// SyncError represents a sync error
+type SyncError struct {
+	Timestamp time.Time `json:"timestamp"`
+	Message   string    `json:"message"`
+}
+
+// GetInfo returns sync information for modal
+// GET /api/sync/info
+func (h *SyncHandler) GetInfo(c *gin.Context) {
+	// Check online status by pinging MariaDB
+	isOnline := h.checkOnline()
+
+	// Get sync times
+	lastPricelistSync := h.localDB.GetLastSyncTime()
+
+	// Get error count (only changes with LastError != "")
+	errorCount := int(h.localDB.CountErroredChanges())
+
+	// Get recent errors (last 10)
+	changes, err := h.localDB.GetPendingChanges()
+	if err != nil {
+		slog.Error("failed to get pending changes for sync info", "error", err)
+		// Even if we can't get changes, we can still return the error count
+		c.JSON(http.StatusOK, SyncInfoResponse{
+			LastSyncAt: lastPricelistSync,
+			IsOnline:   isOnline,
+			ErrorCount: errorCount,
+			Errors:     []SyncError{}, // Return empty errors list
+		})
+		return
+	}
+
+	var errors []SyncError
+	for _, change := range changes {
+		// Check if there's a last error and it's not empty
+		if change.LastError != "" {
+			errors = append(errors, SyncError{
+				Timestamp: change.CreatedAt,
+				Message:   change.LastError,
+			})
+		}
+	}
+
+	// Limit to last 10 errors
+	if len(errors) > 10 {
+		errors = errors[:10]
+	}
+
+	c.JSON(http.StatusOK, SyncInfoResponse{
+		LastSyncAt: lastPricelistSync,
+		IsOnline:   isOnline,
+		ErrorCount: errorCount,
+		Errors:     errors,
+	})
+}
+
 // SyncStatusPartial renders the sync status partial for htmx
 // GET /partials/sync-status
 func (h *SyncHandler) SyncStatusPartial(c *gin.Context) {