feat: serve derivative files via GET /assets/{id}/derivatives/{profile}

- ReadDerivativeHandler queries DerivativeRepository + FileStoragePort
- Profile URL param: thumbnail, thumbnail_large, web_optimized, video_sd
- Immutable cache headers (derivatives don't change once generated)
- Wired into bootstrap catalog service builder

crates/presentation/src/state.rs

@@ -2,8 +2,8 @@ use std::sync::Arc;
 
 use application::{
     catalog::{
-        GetAssetHandler, GetTimelineHandler, ReadAssetFileHandler, RegisterAssetHandler,
-        UpdateMetadataHandler,
+        GetAssetHandler, GetTimelineHandler, ReadAssetFileHandler, ReadDerivativeHandler,
+        RegisterAssetHandler, UpdateMetadataHandler,
     },
     identity::{GetProfileHandler, LoginUserHandler, RegisterUserHandler},
     organization::{
@@ -41,6 +41,7 @@ pub struct CatalogHandlers {
     pub get_timeline: Arc<GetTimelineHandler>,
     pub update_metadata: Arc<UpdateMetadataHandler>,
     pub read_asset_file: Arc<ReadAssetFileHandler>,
+    pub read_derivative: Arc<ReadDerivativeHandler>,
     pub register_asset: Arc<RegisterAssetHandler>,
 }