feat: frontend-ready backend — pagination, auto-derivatives, list endpoints, bulk ops, OpenAPI

Pagination: count_by_owner + count_search on AssetRepository,
timeline/search return real total count (not page len).

Auto-derivatives: worker enqueues GenerateDerivative when
ExtractMetadata job completes, closing the upload→thumbnail gap.

List endpoints: GET /albums, GET /stacks with user scoping.
ListAlbumsHandler, ListStacksHandler, find_by_owner on AssetStackRepository.

Tag filtering: tag_name field on AssetFilters, JOIN asset_tags+tags
in postgres search/count queries.

Bulk operations: POST /assets/bulk-delete, POST /assets/bulk-tag.

Album update: PUT /albums/{id} with UpdateAlbumHandler (title, description).

OpenAPI: utoipa annotations on all 47 endpoints + all request/response
schemas registered. Scalar UI at /scalar covers full API.

crates/application/src/organization/commands/mod.rs

@@ -1,7 +1,9 @@
 pub mod create_album;
 pub mod manage_album_entries;
 pub mod tag_asset;
+pub mod update_album;
 
 pub use create_album::{CreateAlbumCommand, CreateAlbumHandler};
 pub use manage_album_entries::{AlbumAction, ManageAlbumEntriesCommand, ManageAlbumEntriesHandler};
 pub use tag_asset::{TagAssetCommand, TagAssetHandler};
+pub use update_album::{UpdateAlbumCommand, UpdateAlbumHandler};

crates/application/src/organization/commands/update_album.rs

@@ -0,0 +1,44 @@
+use domain::{errors::DomainError, ports::AlbumRepository, value_objects::SystemId};
+use std::sync::Arc;
+
+pub struct UpdateAlbumCommand {
+    pub album_id: SystemId,
+    pub user_id: SystemId,
+    pub title: Option<String>,
+    pub description: Option<String>,
+}
+
+pub struct UpdateAlbumHandler {
+    album_repo: Arc<dyn AlbumRepository>,
+}
+
+impl UpdateAlbumHandler {
+    pub fn new(album_repo: Arc<dyn AlbumRepository>) -> Self {
+        Self { album_repo }
+    }
+
+    pub async fn execute(
+        &self,
+        cmd: UpdateAlbumCommand,
+    ) -> Result<domain::entities::Album, DomainError> {
+        let mut album = self
+            .album_repo
+            .find_by_id(&cmd.album_id)
+            .await?
+            .ok_or_else(|| DomainError::NotFound("Album not found".into()))?;
+
+        if album.creator_user_id != cmd.user_id {
+            return Err(DomainError::Forbidden("Not your album".into()));
+        }
+
+        if let Some(title) = cmd.title {
+            album.title = title;
+        }
+        if let Some(desc) = cmd.description {
+            album.description = desc;
+        }
+
+        self.album_repo.save(&album).await?;
+        Ok(album)
+    }
+}

crates/application/src/organization/mod.rs

@@ -4,4 +4,6 @@ pub mod queries;
 pub use commands::{AlbumAction, ManageAlbumEntriesCommand, ManageAlbumEntriesHandler};
 pub use commands::{CreateAlbumCommand, CreateAlbumHandler};
 pub use commands::{TagAssetCommand, TagAssetHandler};
+pub use commands::{UpdateAlbumCommand, UpdateAlbumHandler};
 pub use queries::get_album::{GetAlbumHandler, GetAlbumQuery};
+pub use queries::list_albums::{ListAlbumsHandler, ListAlbumsQuery};

crates/application/src/organization/queries/list_albums.rs

@@ -0,0 +1,22 @@
+use domain::{
+    entities::Album, errors::DomainError, ports::AlbumRepository, value_objects::SystemId,
+};
+use std::sync::Arc;
+
+pub struct ListAlbumsQuery {
+    pub user_id: SystemId,
+}
+
+pub struct ListAlbumsHandler {
+    album_repo: Arc<dyn AlbumRepository>,
+}
+
+impl ListAlbumsHandler {
+    pub fn new(album_repo: Arc<dyn AlbumRepository>) -> Self {
+        Self { album_repo }
+    }
+
+    pub async fn execute(&self, query: ListAlbumsQuery) -> Result<Vec<Album>, DomainError> {
+        self.album_repo.find_by_creator(&query.user_id).await
+    }
+}

crates/application/src/organization/queries/mod.rs

@@ -1 +1,2 @@
 pub mod get_album;
+pub mod list_albums;