refactor(services): add file_lifecycle and blob_lifecycle

- complete src/application/ports/blob_lifecycle.rs with traits:
    * BlobCreationHook
    * BlobDeletionHook

 - add src/application/ports/file_lifecycle.rs with traits:
    * FileCreatedHook
    * FileDeletedHook
    * FileUpdatedHook

src/application/ports/file_lifecycle.rs

@@ -0,0 +1,57 @@
+use std::future::Future;
+use std::pin::Pin;
+
+/// Observer notified by [`FileUploadService`] when a new file record is created
+/// (including dedup hits where the blob already exists).
+///
+/// Register with [`FileUploadService::with_file_created_hook`] during DI wiring.
+pub trait FileCreatedHook: Send + Sync {
+    /// Called after the file record has been persisted.
+    /// `file_id` — opaque file UUID string.
+    /// `blob_hash` — BLAKE3 hex of the blob (may already exist on disk for dedup hits).
+    /// `content_type` — MIME type of the content.
+    /// Must be best-effort — must not propagate errors.
+    fn on_file_created<'a>(
+        &'a self,
+        file_id: &'a str,
+        blob_hash: &'a str,
+        content_type: &'a str,
+    ) -> Pin<Box<dyn Future<Output = ()> + Send + 'a>>;
+}
+
+/// Observer notified by [`FileUploadService`] when an existing file's blob is
+/// replaced (WebDAV PUT overwrite, WOPI PutFile, Nextcloud chunked upload).
+///
+/// Implement this trait on any service that needs to react to a content swap
+/// (e.g. thumbnail invalidation + regeneration, search index update).
+/// Register with [`FileUploadService::with_file_updated_hook`] during DI wiring.
+///
+/// The boxed-future return keeps the trait dyn-compatible so multiple
+/// implementations can be stored as `Vec<Arc<dyn FileUpdatedHook>>`.
+pub trait FileUpdatedHook: Send + Sync {
+    /// Called after the new blob has been stored and the file record updated.
+    ///
+    /// `file_id` is an opaque file UUID string, `blob_hash` is the BLAKE3 hex
+    /// of the new blob, `content_type` is the MIME type of the new content.
+    /// Must be best-effort — must not propagate errors.
+    fn on_file_updated<'a>(
+        &'a self,
+        file_id: &'a str,
+        blob_hash: &'a str,
+        content_type: &'a str,
+    ) -> Pin<Box<dyn Future<Output = ()> + Send + 'a>>;
+}
+
+/// Observer notified by [`FileManagementService`] when a file is permanently
+/// deleted (either directly or after being emptied from trash).
+///
+/// Register with [`FileManagementService::with_file_deleted_hook`] during DI wiring.
+pub trait FileDeletedHook: Send + Sync {
+    /// Called after the file record has been removed.
+    /// `file_id` — opaque file UUID string.
+    /// Must be best-effort — must not propagate errors.
+    fn on_file_deleted<'a>(
+        &'a self,
+        file_id: &'a str,
+    ) -> Pin<Box<dyn Future<Output = ()> + Send + 'a>>;
+}