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/adapters/mod.rs

@@ -0,0 +1,11 @@
+//! Infrastructure Adapters
+//! 
+//! This module contains adapters that bridge the gap between domain repositories
+//! and application ports. These adapters implement the application layer ports
+//! using the infrastructure layer repositories.
+
+pub mod calendar_storage_adapter;
+pub mod contact_storage_adapter;
+
+pub use calendar_storage_adapter::CalendarStorageAdapter;
+pub use contact_storage_adapter::ContactStorageAdapter;