[PB-6608] feat/add favorites support for files and folders

[victor-ferro]

Description

Adds SDK support for the new Favorites feature in the Drive API (drive-server-wip).

New methods in the Storage class:

Endpoint	Method
PUT /files/{uuid}/favorite	markFileAsFavorite(uuid)
DELETE /files/{uuid}/favorite	unmarkFileAsFavorite(uuid)
GET /files/favorites	getFavoriteFiles(payload) (cancellable)
PUT /folders/{uuid}/favorite	markFolderAsFavorite(uuid)
DELETE /folders/{uuid}/favorite	unmarkFolderAsFavorite(uuid)
GET /folders/favorites	getFavoriteFolders(payload) (cancellable)

New types in drive/storage/types.ts: FavoriteStatusResponse, FavoriteFileDto,
FavoriteFolderDto, GetFavoriteFilesPayload, GetFavoriteFoldersPayload. The
paginated folder-content types and the hand-written item interfaces now expose an
optional isFavorite?: boolean returned by the backend.

Includes unit tests for all six methods following the existing request-shape pattern.

Notes

The backend PR adding isFavorite to the API is not deployed to production yet, so the
generated src/schema.ts does not include the field. This PR bridges that gap with
manual & { isFavorite?: boolean } intersections on the schema-derived types — safe to
ship before and after the backend deploy.

Once the backend is live in production, I have a follow-up PR already prepared that runs
yarn swagger (the production spec will then document isFavorite and the favorites
endpoints) and reverts those intersections to plain schema-derived aliases. Already
verified locally against the updated backend: types compile and tests pass without the
intersections.