A blank note can show a page-background template painted behind the
ink, picked from the toolbar and persisted per notebook.
- NoteBackground: blank / dots / ruled / grid / cornell, drawn in
page space (scales with zoom), subtle grey. Cornell = left margin +
bottom summary rule over a ruled body.
- Stored as the enum name in the notebook sidecar (back-compat:
missing/unknown -> blank), saved/loaded via SidecarRepository so it
restores on reopen.
- Picker added to the note tool palette.
PDF backgrounds skipped (PDFs have their own page content). analyze
clean, 386 tests green.
