feat: safe deletion, album/asset delete, trash, README update

- volume-aware deletion: read-only volumes remove DB only, writable
  volumes soft-delete to trash with configurable grace period
- trash page with restore, worker purge sweep (TRASH_RETENTION_DAYS)
- album delete endpoint + sidebar trash icon
- asset delete from timeline selection toolbar
- all listing queries exclude trashed assets (deleted_at IS NULL)
- timeline ordered by EXIF capture date, date-summary endpoint
- README rewritten with features, setup, full env var table

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

@@ -1,9 +1,11 @@
 pub mod create_album;
+pub mod delete_album;
 pub mod manage_album_entries;
 pub mod tag_asset;
 pub mod update_album;
 
 pub use create_album::{CreateAlbumCommand, CreateAlbumHandler};
+pub use delete_album::{DeleteAlbumCommand, DeleteAlbumHandler};
 pub use manage_album_entries::{AlbumAction, ManageAlbumEntriesCommand, ManageAlbumEntriesHandler};
 pub use tag_asset::{TagAssetCommand, TagAssetHandler};
 pub use update_album::{UpdateAlbumCommand, UpdateAlbumHandler};