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/application/services/i18n_application_service.rs

@@ -51,7 +51,6 @@ impl I18nApplicationService {
     }
     
     /// Load translations for all available locales
-    #[allow(dead_code)]
     pub async fn load_all_translations(&self) -> Vec<(Locale, I18nResult<()>)> {
         let locales = self.i18n_service.available_locales().await;
         let mut results = Vec::new();
@@ -70,7 +69,6 @@ impl I18nApplicationService {
     }
     
     /// Check if a locale is supported
-    #[allow(dead_code)]
     pub async fn is_supported(&self, locale: Locale) -> bool {
         self.i18n_service.is_supported(locale).await
     }