feat(bulk): My DXCC / My CQ zone / My ITU zone

The My-station group covered nineteen fields and not the three numeric ones.
They take their own integer path rather than the generic text setter: the
columns are nullable integers, and while SQLite would coerce '14' quietly, a
shared MySQL logbook would not — and empty must become NULL, never ''. Bounds
checked (DXCC <1000, CQ 1-40, ITU 1-90) so a slip cannot stamp zone 400 across
a thousand rows.

internal/qso/qso.go

@@ -868,6 +868,44 @@ var bulkEditableCols = map[string]bool{
 
 // BulkSetField sets one whitelisted column to value on every listed QSO in a
 // single statement. value "" clears the field. Returns rows affected.
+// bulkEditableIntCols are the NUMERIC columns the bulk editor may touch. Their
+// own path, not the text one: the columns are nullable integers, and while
+// SQLite would coerce "14" quietly, a shared MySQL logbook would not — and an
+// empty string is NULL here, never "".
+var bulkEditableIntCols = map[string]bool{
+	"my_dxcc":     true,
+	"my_cq_zone":  true,
+	"my_itu_zone": true,
+}
+
+// BulkSetIntField sets one integer column across the ids; v nil clears it.
+func (r *Repo) BulkSetIntField(ctx context.Context, ids []int64, column string, v *int) (int64, error) {
+	if !bulkEditableIntCols[column] {
+		return 0, fmt.Errorf("field %q is not bulk-editable", column)
+	}
+	if len(ids) == 0 {
+		return 0, nil
+	}
+	ph := make([]string, len(ids))
+	args := make([]any, 0, len(ids)+2)
+	var val any
+	if v != nil {
+		val = *v
+	}
+	args = append(args, val, db.NowISO())
+	for i, id := range ids {
+		ph[i] = "?"
+		args = append(args, id)
+	}
+	res, err := r.db.ExecContext(ctx,
+		"UPDATE qso SET "+column+" = ?, updated_at = ? WHERE id IN ("+strings.Join(ph, ",")+")", args...)
+	if err != nil {
+		return 0, fmt.Errorf("bulk set %s: %w", column, err)
+	}
+	n, _ := res.RowsAffected()
+	return n, nil
+}
+
 func (r *Repo) BulkSetField(ctx context.Context, ids []int64, column, value string) (int64, error) {
 	if !bulkEditableCols[column] {
 		return 0, fmt.Errorf("field %q is not bulk-editable", column)