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/metadata.rs

@@ -413,7 +413,7 @@ pub async fn approve_metadata(
 pub async fn reject_metadata(
     State(state): State<AppState>,
     AxumPath(id): AxumPath<Uuid>,
-) -> Result<Json<serde_json::Value>, ApiError> {
+) -> Result<Json<crate::responses::StatusResponse>, ApiError> {
     let result = sqlx::query(
         "UPDATE external_metadata_links SET status = 'rejected', updated_at = NOW() WHERE id = $1",
     )
@@ -425,7 +425,7 @@ pub async fn reject_metadata(
         return Err(ApiError::not_found("link not found"));
     }
 
-    Ok(Json(serde_json::json!({"status": "rejected"})))
+    Ok(Json(crate::responses::StatusResponse::new("rejected")))
 }
 
 // ---------------------------------------------------------------------------
@@ -571,7 +571,7 @@ pub async fn get_missing_books(
 pub async fn delete_metadata_link(
     State(state): State<AppState>,
     AxumPath(id): AxumPath<Uuid>,
-) -> Result<Json<serde_json::Value>, ApiError> {
+) -> Result<Json<crate::responses::DeletedResponse>, ApiError> {
     let result = sqlx::query("DELETE FROM external_metadata_links WHERE id = $1")
         .bind(id)
         .execute(&state.pool)
@@ -581,7 +581,7 @@ pub async fn delete_metadata_link(
         return Err(ApiError::not_found("link not found"));
     }
 
-    Ok(Json(serde_json::json!({"deleted": true, "id": id.to_string()})))
+    Ok(Json(crate::responses::DeletedResponse::new(id)))
 }
 
 // ---------------------------------------------------------------------------