Fix vCard import silently dropping properties with a non-item group prefix - #10271

Problem

RFC 6350 permits any group name as a group. prefix on a vCard property (e.g. HOME.EMAIL:..., group1.TEL:...). Roundcube only recognized Apple's item\d. prefix, so a property carrying any other group prefix was silently dropped on import: the email/phone/etc. never appeared in the parsed record.

Root cause

rcube_vcard::cleanup() (program/lib/Roundcube/rcube_vcard.php:608) stripped only the item\d*. prefix from property lines. Any surviving group. prefix (e.g. HOME.EMAIL) was carried into vcard_decode(), which then keyed the value under the literal field name HOME.EMAIL instead of EMAIL. Since that field is not in the fieldmap, the value was discarded.

Fix

Generalize the prefix-stripping regex in cleanup() from /^item\d*\./mi to /^[a-z0-9-]+\./mi, so any RFC 6350 group prefix at the start of a line is removed before decoding. This runs after the existing Apple-specific X-ABRELATEDNAMES / X-ABLabel handling and after the item\d*.X-AB* cruft removal, so item-prefixed Apple label pairing is unaffected. Group names never contain dots and continuation lines begin with whitespace, so the pattern only matches genuine group prefixes.

Testing

Added test_parse_group_prefix in tests/Framework/VCardTest.php, importing a vCard with HOME.EMAIL: and group1.TEL: and asserting both are parsed into the record ($vcard->email[0], and email:other / phone:other in get_assoc()). The test fails on unmodified code and passes after the fix. The full VCardTest suite (15 tests, incl. the existing ITEM1.-prefixed address case) passes, and phpstan level 4 reports no new errors.