Addresses argus review comment 90297 on PR #4899:
- swarm-controller/README.md: list the three DELETE routes (including
matrix's ?revoke=true) beside the PUT/GET ones already documented.
- LinkedAccounts.tsx: a delete answering 404 means the account is
already gone, so treat it as the delete's end state — re-fetch and
close the dialog instead of showing an error.
- matrix_account.rs: matrix_logout treats a 401 M_UNKNOWN_TOKEN as the
token already being revoked and proceeds with the delete; every
other logout failure still keeps the account. Adds unit tests and
updates docs/swarm/ui.md to match.
b90be9e65e