Fix token handling, modal behavior, and pagination

Multiple fixes and improvements:

- src/app/api/user/hardcover-shelves/[id]/route.ts: Make token testing more robust by using the existing shelf.apiToken when no new token is provided, attempt decryption only when needed, and gracefully fall back on decryption errors.
- src/components/ui/AddShelfModal.tsx: Simplify token handling by passing the trimmed token directly to addHardcover (remove client-side 'Bearer ' stripping).
- src/components/ui/ManageShelfModal.tsx: Stabilize form reset effect by depending on shelf?.id to avoid unnecessary re-renders when the shelf object changes identity.
- src/components/ui/Modal.tsx: Simplify modal rendering by removing the mounted state and createPortal usage, cleaning up imports and rendering directly.
- src/lib/services/hardcover-api.service.ts: Add a logger, introduce a MAX_PAGES cap and page counters to prevent unbounded pagination loops, and log/break when the API returns errors during pagination.

These changes improve reliability (token handling and pagination safety), reduce unnecessary renders, and simplify modal lifecycle.

src/components/ui/ManageShelfModal.tsx

@@ -26,14 +26,14 @@ export function ManageShelfModal({ shelf, isOpen, onClose }: ManageShelfModalPro
   const { updateShelf: updateGoodreads, isLoading: isUpdatingGoodreads, error: goodreadsError } = useUpdateGoodreadsShelf();
   const { updateShelf: updateHardcover, isLoading: isUpdatingHardcover, error: hardcoverError } = useUpdateHardcoverShelf();
 
-  // Reset form when shelf changes
+  // Reset form when shelf changes (use shelf?.id for stable reference)
   React.useEffect(() => {
     if (shelf) {
       setRssUrl(shelf.type === 'goodreads' ? shelf.sourceId : '');
       setListId(shelf.type === 'hardcover' ? shelf.sourceId : '');
       setApiToken('');
     }
-  }, [shelf]);
+  }, [shelf?.id]);
 
   if (!shelf) return null;