feat: add ContactStore, the vCard address-book parse

Reads a vdirsyncer contacts directory of vCard 3.0 files into a
QList<Contact> for the completion work that follows. Pure over values,
no widget and no QCompleter, so the parse is testable without a window.

unfold() joins folded lines before any field is looked at; parseCard()
splits property from value on the first colon outside a quoted
parameter, unescapes FN, and yields one contact per EMAIL line;
loadDirectory() walks recursively, skips unreadable or addressless
cards, de-duplicates on the address case-insensitively, and sorts by
name then address. N, PHOTO, ADR and TEL are deliberately not used.

23 new tests. No user-facing strings, so no tr() change.

0 files changed, 0 insertions, 0 deletions