fix(ocm): OCM token refresh and remote detection

[MahdiBaghbani]

This PR is a part of cs3org/OCM-STA#16

Summary

This work improves OCM interoperability when Nextcloud federates with a Reva peer that supports the authorization code flow.

Bearer tokens obtained through OCM exchange are now stored in the dedicated access-token fields (with persisted expiry), and are reloaded when external shares are remounted. They are no longer carried via the legacy password path.

Token refresh honors the expiry signaled by the sender, avoids duplicate refresh when another process has already renewed the token, and applies backoff on repeated exchange attempts so a failing refresh does not overload the remote token endpoint.

After refresh, cloud-federation share metadata stays consistent with the live OCM response (share URI, permissions, and related fields). status.php handling is tightened so a Reva-branded response is not classified as an ownCloud-style peer when it is not, while legitimate OCM discovery continues to succeed.

There is also a complementary PR in Reva as well cs3org/reva#5552

Motivation

The issues above appeared in end-to-end testing against a code-flow-capable Reva. Addressing status.php misclassification on the Nextcloud side avoids depending on a long-lived Reva-side status.php compatibility shim.

For Enrique

This PR is against your branch because that is where the work should land first. You already have a PR from that branch into nextcloud/server master, so once you fold this in, the same commits should show up in that upstream PR without opening a parallel PR from my fork.

[enriquepablo]

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