refactor: Phase E — types de réponses API standardisés + SVGs inline → Icon

E1 - API responses:
- Crée responses.rs avec OkResponse, DeletedResponse, UpdatedResponse,
  RevokedResponse, UnlinkedResponse, StatusResponse (6 tests de sérialisation)
- Remplace ~15 json!() inline par des types structurés dans books, libraries,
  tokens, users, handlers, anilist, metadata, download_detection, torrent_import
- Signatures de retour des handlers typées (plus de serde_json::Value)

E2 - SVGs → Icon component:
- Ajoute icon "lock" au composant Icon
- Remplace ~30 SVGs inline par <Icon> dans 9 composants
  (FolderPicker, FolderBrowser, LiveSearchForm, JobRow, LibraryActions,
  ReadingStatusModal, EditBookForm, EditSeriesForm, UserSwitcher)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/api/src/anilist.rs

@@ -433,7 +433,7 @@ pub async fn link_series(
 pub async fn unlink_series(
     State(state): State<AppState>,
     Path((library_id, series_name)): Path<(Uuid, String)>,
-) -> Result<Json<serde_json::Value>, ApiError> {
+) -> Result<Json<crate::responses::UnlinkedResponse>, ApiError> {
     let result = sqlx::query(
         "DELETE FROM anilist_series_links WHERE library_id = $1 AND series_name = $2",
     )
@@ -446,7 +446,7 @@ pub async fn unlink_series(
         return Err(ApiError::not_found("AniList link not found"));
     }
 
-    Ok(Json(serde_json::json!({"unlinked": true})))
+    Ok(Json(crate::responses::UnlinkedResponse::new()))
 }
 
 /// Toggle AniList sync for a library