feat(#113): 100% blob storage model — PostgreSQL metadata + DedupService blobs

BREAKING CHANGE: Storage model completely rewritten. All file/folder
metadata now lives in PostgreSQL (storage schema). File content stored
as content-addressable blobs via DedupService. Filesystem directories
are no longer used for user storage.

New components:
- storage.folders / storage.files / storage.trash_items (PG schema)
- FolderDbRepository: virtual folders backed by PG
- FileBlobReadRepository: file reads via PG metadata + dedup blobs
- FileBlobWriteRepository: file writes via PG metadata + dedup blobs
- TrashDbRepository: soft-delete trash using is_trashed flags

Removed legacy FS components (~5500 lines deleted):
- FolderFsRepository, FileFsReadRepository, FileFsWriteRepository
- CompositeFileRepository, ParallelFileProcessor
- IdMappingService, IdMappingOptimizer, FileMetadataCache
- BufferPool, FileSystemUtils, RepositoryErrors
- TrashFsRepository, FolderFsRepositoryTrash

DI rewired: build_app_state() now requires PgPool (no FS fallback).
FileUploadService.new_with_read() and FileRetrievalService.new_with_cache()
constructors added for blob model (no write-behind needed).

Closes #113

src/infrastructure/repositories/mod.rs

@@ -1,21 +1,10 @@
-pub mod folder_fs_repository;
-pub mod parallel_file_processor;
-pub mod repository_errors;
-
-// Repositorios CQRS (Read/Write) + composite
-pub mod composite_file_repository;
-pub mod file_fs_read_repository;
-pub mod file_fs_write_repository;
-
-pub mod folder_fs_repository_trash;
 pub mod share_fs_repository;
-pub mod trash_fs_repository;
 
-// Repositorios PostgreSQL
+// Repositorios PostgreSQL (blob-storage model)
 pub mod pg;
 
 // Re-exportar para facilitar acceso
-pub use composite_file_repository::CompositeFileRepository;
-pub use file_fs_read_repository::FileFsReadRepository;
-pub use file_fs_write_repository::FileFsWriteRepository;
-pub use pg::{SessionPgRepository, UserPgRepository};
+pub use pg::{
+    FileBlobReadRepository, FileBlobWriteRepository, FolderDbRepository,
+    SessionPgRepository, TrashDbRepository, UserPgRepository,
+};