feat(docs): put-xlsx with excelize cutover workbook

Add internal/xlspipe (github.com/xuri/excelize/v2) and oo docs put-xlsx
to generate multi-sheet budgets with named inputs, SUM/AVG/MIN formulas,
cross-sheet links, Russian labels, and cell comments for OnlyOffice.

Template cutover-portugal: sheets Ввод, Вс 6.09, Чт 3.09, Ср гип, Сводка.
Upload via UploadProjectFileReplacing (--replace default).

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/xlspipe/template.go

@@ -0,0 +1,26 @@
+package xlspipe
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/xuri/excelize/v2"
+)
+
+// Template names for oo docs put-xlsx --template.
+const (
+	TemplateCutoverPortugal = "cutover-portugal"
+)
+
+// BuildTemplate returns an xlsx workbook for a known template name.
+func BuildTemplate(name string) (*File, error) {
+	switch strings.ToLower(strings.TrimSpace(name)) {
+	case TemplateCutoverPortugal, "portugal-cutover", "cutover":
+		return BuildCutoverPortugalWorkbook(DefaultCutoverPortugal())
+	default:
+		return nil, fmt.Errorf("unknown xlsx template %q (try: %s)", name, TemplateCutoverPortugal)
+	}
+}
+
+// File is an alias so cmd/oo can refer to excelize.File without importing excelize in every handler.
+type File = excelize.File