fix(ebook-reader): load SVG images and fix progress update ID

- Add SVG image support: process <image xlink:href=...> elements
  in addition to HTML <img> tags for cover pages and embedded images
- Fix progress update: use 'id' from API response instead of
  'media_item_id' which the backend never returns for this endpoint
- Update reader context interfaces to include currentPage field
- Add debug logging for all resource keys to help troubleshoot
  image loading issues in future epubs

web/src/types/reader.d.ts

@@ -72,7 +72,7 @@ interface ParserCapabilities {
 // ============================================================
 
 interface ReaderMetadata {
-  media_item_id: string;
+  id: string;
   title: string;
   author: string;
   cover_image_path: string;