feat(core): import_lastpass parser — happy-path Login

Pins the parse_lastpass_csv signature and ImportWarning shape.
A single LastPass row with name/url/username/password round-trips
to a Login item with a freshly-minted ID. Header validation
rejects shape mismatches with a clear message.

TOTP, grouping, fav, SecureNote rows, and error paths land in
Tasks 3-6.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

crates/relicario-core/src/lib.rs

@@ -80,3 +80,6 @@ pub mod imgsecret;
 
 pub mod backup;
 pub use backup::{pack_backup, unpack_backup, BackupInput, BackupOutput, BackupItem, BackupAttachment};
+
+pub mod import_lastpass;
+pub use import_lastpass::{parse_lastpass_csv, ImportWarning};