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/calendar_pg_repository.rs

@@ -1,12 +1,11 @@
 use async_trait::async_trait;
 use chrono::Utc;
-use sqlx::{PgPool, query, query_as, Row, types::Uuid};
+use sqlx::{PgPool, Row, types::Uuid};
 use std::sync::Arc;
 
 use crate::domain::entities::calendar::Calendar;
 use crate::domain::repositories::calendar_repository::{CalendarRepository, CalendarRepositoryResult};
-use crate::common::errors::{DomainError, ErrorContext};
-use sqlx::Transaction;
+use crate::common::errors::DomainError;
 
 pub struct CalendarPgRepository {
     pool: Arc<PgPool>,