Add smart self-healing for sync errors

Implements automatic repair mechanism for pending changes with sync errors:
- Projects: validates and fixes empty name/code fields
- Configurations: ensures project references exist or assigns system project
- Clears errors and resets attempts to give changes another sync chance

Backend:
- LocalDB.RepairPendingChanges() with smart validation logic
- POST /api/sync/repair endpoint
- Detailed repair results with remaining errors

Frontend:
- Auto-repair section in sync modal shown when errors exist
- "ИСПРАВИТЬ" button with clear explanation of actions
- Real-time feedback with result messages

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

internal/handlers/sync.go

@@ -419,6 +419,26 @@ func (h *SyncHandler) GetPendingChanges(c *gin.Context) {
 	})
 }
 
+// RepairPendingChanges attempts to repair errored pending changes
+// POST /api/sync/repair
+func (h *SyncHandler) RepairPendingChanges(c *gin.Context) {
+	repaired, remainingErrors, err := h.localDB.RepairPendingChanges()
+	if err != nil {
+		slog.Error("repair pending changes failed", "error", err)
+		c.JSON(http.StatusInternalServerError, gin.H{
+			"success": false,
+			"error":   err.Error(),
+		})
+		return
+	}
+
+	c.JSON(http.StatusOK, gin.H{
+		"success":          true,
+		"repaired":         repaired,
+		"remaining_errors": remainingErrors,
+	})
+}
+
 // SyncInfoResponse represents sync information for the modal
 type SyncInfoResponse struct {
 	// Connection