docs: update documentation to reflect 100% blob storage model

Rewrite documentation to match the new architecture where all
file metadata lives in PostgreSQL and content is stored as
content-addressed blobs via DedupService.

Updated files:
- internal-architecture.md: complete rewrite — new DB schema,
  blob repos (FolderDb, FileBlobRead/Write, TrashDb), updated
  DI container, service groups, architecture diagram, data flows
- file-system-safety.md: repurposed as storage-safety.md —
  covers PostgreSQL ACID guarantees + DedupService atomic writes
- caching-architecture.md: updated repo references to blob repos,
  removed write-behind cache section, updated upload/download flows
- trash-feature-summary.md: rewritten for soft-delete model
  (is_trashed flag, trash_items VIEW, TrashDbRepository)
- share-integration.md: clarified ShareFsRepository scope,
  updated DI snippet, added blob storage context note
- deduplication.md: updated DI snippet (dedup injected into repos)
- deployment.md: updated feature matrix (file storage requires DB)
- important-delta-sync-implementation.md: updated DI references

Removed legacy references: IdMappingPort, StorageMediator,
WriteBehindCache, FsFileRepository, FsFolderRepository,
TrashFsRepository, folder_ids.json, file_ids.json.

doc/important-delta-sync-implementation.md

@@ -462,7 +462,7 @@ src/
 │           └── delta_sync_handler.rs   # NUEVO: Endpoints API
 │
 └── common/
-    └── di.rs                           # Añadir: delta_sync_service a CoreServices
+    └── di.rs                           # Añadir: delta_sync_service a AppState
 ```
 
 ### Main service (delta_sync_service.rs)
@@ -1133,7 +1133,7 @@ thiserror = "1.0"     # Para errores tipados (probablemente ya existe)
 - [ ] Implement **generate_delta()**
 - [ ] Implement **apply_delta()**
 - [ ] Create handler and API endpoints
-- [ ] Integrate into DI (**CoreServices**)
+- [ ] Integrate into DI (**AppState**)
 - [ ] Add routes in `routes.rs`
 - [ ] Integrate with upload (automatic indexing)
 - [ ] Integrate with delete (signature cleanup)