fix: critical bugs from deep audit

- Fix copy_files() data loss: implement real copy_file across full stack
  (FileWritePort, FileManagementUseCase, stubs, service, repository with
  atomic CTE + dedup ref_count increment, batch_operations caller)
- Fix plaintext password in replace_default_admin: hash password via
  PasswordHasherPort before User::new()
- Fix CalendarService hardcoded user_id: unify CalendarUseCase trait with
  explicit user_id parameter on all methods, remove zombie _for_user
  duplicates and hardcoded 'current_user_id', update 20 CalDAV handler
  call sites
- Previous session: migrate DedupService to PostgreSQL (storage.blobs),
  atomic CTEs with compensation for file/folder repository operations

src/infrastructure/repositories/mod.rs

@@ -5,6 +5,6 @@ pub mod pg;
 
 // Re-exportar para facilitar acceso
 pub use pg::{
-    FileBlobReadRepository, FileBlobWriteRepository, FolderDbRepository,
-    SessionPgRepository, TrashDbRepository, UserPgRepository,
+    FileBlobReadRepository, FileBlobWriteRepository, FolderDbRepository, SessionPgRepository,
+    TrashDbRepository, UserPgRepository,
 };