Adds a read-only example that exercises the connector against a real
Nextcloud: Login Flow v2, PROPFIND listing, the Depth:0 ETag pruning
probe, a 256KB range GET, and a server preview request. No PUT, MOVE or
DELETE, so it cannot alter a live library.
Running it against nextcloud.tourolle.paris (34.0.2) surfaced a real API
flaw rather than an example bug. The crypto provider was installed in
NextcloudBackend::new, but authentication necessarily runs *before* a
backend exists — so any caller following the documented flow panicked on
the first client build. Every entry point now goes through
`http_client()`, which installs the provider first, and auth gains
`begin_default()` for callers with no client yet. A test builds a client
without a backend to keep the regression out.
Also populates RawImage::crop from rawler's crop_area/active_area and
re-phases the CFA pattern when the crop origin is odd — cropping to the
active area without that swaps red and blue.
Login Flow v2 confirmed working against the live server: the flow URL is
issued and the poll endpoint responds. The remaining checks need a
browser approval, so they run interactively.
88 tests passing.
dtourolle
fbadf9afc8