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.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index b933f3d..26314dc 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -42,6 +42,7 @@ add_library(qtmaildir_lib STATIC
     querycompleter.cpp
     rulequery.cpp
     searchterm.cpp
+    contactstore.cpp
     signatures.cpp
 )