add CJK auto-wrap support for text watermarks (#1427)

* add CJK auto-wrap support for text watermarks

# Conflicts:
#	pkg/pdfcpu/model/text.go
#	pkg/pdfcpu/stamp.go

* fix CJK text overflow causing font size shrinkage by breaking oversized words via wrapLine; add CJK line-breaking tests; update MaxWidth field comment

* pre-wrap text with WordWrap so maxWidth no longer affects font scaling or bounding box
* adapt CJK watermark changes to latest upstream APIs and fix swallowed errors