Clipboard front matter carries over when annotating files

- New: input YAML header overrides the note header in file-annotation mode —
when annotating a non-Tp-Note file (e.g. `tpnote report.pdf`), a YAML header
supplied through the clipboard or stdin now populates the new note's `title:`,
`author:` and `date:` fields (and `keywords:` under the `zettel` scheme)
instead of always deriving them from the filename, the username and the
current date. Missing fields fall back to those previous defaults, so
behaviour is unchanged when no header is supplied. Because the title is taken
from the header, the new note's filename follows it as well.
- Maintenance: upgraded compatible dependencies (clipboard-rs 0.3.5,
time 0.3.53, html-escape 0.2.14); bumped tpnote-lib to v0.46.3.