Add cancellation reason tracking with user/system codes and UI

internal/api/handlers_jobs.go

@@ -2,10 +2,12 @@ package api
 
 import (
 	"database/sql"
+	"encoding/json"
 	"fmt"
 	"net/http"
 	"os"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/go-chi/chi/v5"
@@ -109,11 +111,23 @@ func (h *JobHandler) Cancel(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	var body struct {
+		Reason string `json:"reason"`
+	}
+	if r.Body != nil && r.ContentLength > 0 {
+		_ = json.NewDecoder(r.Body).Decode(&body)
+	}
+	reason := strings.TrimSpace(body.Reason)
+	if reason == "" {
+		reason = "Job was cancelled by user"
+	}
+
 	if h.engine != nil {
-		h.engine.Cancel(id, j.SyncPairID)
+		h.engine.Cancel(id, j.SyncPairID, true)
 	}
 
 	repo.UpdateStatus(id, "cancelled")
+	repo.SetError(id, "cancelled_user", reason)
 	writeJSON(w, map[string]string{"status": "cancelled"})
 }