refactor: remove serde from domain entities for Clean Architecture compliance

- Remove Serialize/Deserialize from File, Folder, Session, User, Contact entities
- Create contact_persistence_dto.rs for JSONB persistence in infrastructure layer
- Update contact_pg_repository to use persistence DTOs
- Fix dependency on zip crate (downgrade from 7.2.0 to 2.1.0)
- Fix unused variable warnings in main.rs
- Move PathService import from domain to infrastructure
- Add missing fields to CoreServices and RepositoryServices
- Create proper service initialization in main.rs

Clean Architecture improvements:
- Domain layer no longer depends on serde framework
- Persistence concerns isolated to infrastructure layer
- TokenClaims in auth_service.rs is only exception (required for JWT)

src/infrastructure/repositories/pg/mod.rs

@@ -2,7 +2,7 @@ mod address_book_pg_repository;
 mod calendar_pg_repository;
 mod calendar_event_pg_repository;
 mod contact_pg_repository;
-mod contact_group_pg_repository;
+mod contact_persistence_dto;
 mod session_pg_repository;
 mod transaction_utils;
 mod user_pg_repository;
@@ -11,6 +11,6 @@ pub use address_book_pg_repository::AddressBookPgRepository;
 pub use calendar_pg_repository::CalendarPgRepository;
 pub use calendar_event_pg_repository::CalendarEventPgRepository;
 pub use contact_pg_repository::ContactPgRepository;
-pub use contact_group_pg_repository::ContactGroupPgRepository;
+pub use contact_persistence_dto::*;
 pub use session_pg_repository::SessionPgRepository;
 pub use user_pg_repository::UserPgRepository;