parseBitwardenCsvFieldLines previously discarded any field line that did not
contain the ': ' delimiter, truncating multiline values like OpenSSH private
keys to only their first line.
Replace the map+filter pipeline with a reduce that accumulates continuation
lines (lines without ': ') into the previous entry's value, joined by '\n'.
This preserves the full private key content through a CSV round-trip.
Fixes: CSV export to import of SSH key items where the private key body was
silently dropped.
rootphantomerandShuai
