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/domain/src/catalog/ports.rs

@@ -38,6 +38,23 @@ pub trait AssetRepository: Send + Sync {
     ) -> Result<Vec<(chrono::NaiveDate, u64)>, DomainError>;
     async fn save(&self, asset: &Asset) -> Result<(), DomainError>;
     async fn delete(&self, id: &SystemId) -> Result<(), DomainError>;
+    async fn soft_delete(
+        &self,
+        id: &SystemId,
+        deleted_by: &SystemId,
+    ) -> Result<(), DomainError>;
+    async fn restore(&self, id: &SystemId) -> Result<(), DomainError>;
+    async fn find_trashed_before(
+        &self,
+        cutoff: chrono::DateTime<chrono::Utc>,
+    ) -> Result<Vec<Asset>, DomainError>;
+    async fn count_trashed(&self, owner_id: &SystemId) -> Result<u64, DomainError>;
+    async fn find_trashed_by_owner(
+        &self,
+        owner_id: &SystemId,
+        limit: u32,
+        offset: u32,
+    ) -> Result<Vec<Asset>, DomainError>;
 }
 
 // --- AssetMetadataRepository ---