retry a linux account in place instead of deleting the person

POST /users/:id/provision-linux, and a terminal button on each user row. One
operation covering three needs that were all previously answered by "delete the
account and make it again":

  backfill  an account created before the feature existed, or while the host was not
            set up for it
  retry     the first attempt failed for something since fixed — the traversable
            ancestor chmod being the one everybody hits once
  re-key    replace authorized_keys with a new public key

Deleting to redo a retryable side effect throws away the password, the dashboards and
everything else keyed to the row.

The provisioning block moves out of create-user into provisionOsAccount, shared by
both entry points for the same reason app-store/members.ts is shaped that way: two
moments, one piece of work.

Found by testing the retry rather than the create: provisionUserDirs re-chmods every
directory including home, and home belongs to the MEMBER after the first successful
run — chmod requires ownership, so it threw EPERM and took every retry down before it
started. Those chmods are now a default for directories being created, not an
assertion about ones that already exist; os-user.ts sets the home's mode through sudo
and is the authority for it.

The route answers 200 with the error in the body, because the interesting cases are
partial: "the account exists and is confined but the keys failed" is not nothing
having happened, and the row shows both halves.

Verified end to end: blocked ancestor reports the chmod and leaves osUser null, the
retry after that chmod succeeds and records the row, and a re-key replaces
authorized_keys without rotating the outbound key.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/servers/api/users/manage-users.ts

@@ -2,6 +2,7 @@ import type { Handler } from 'hono';
 import { getUsers, getUserById, updateUser, deleteUser, USER_ROLES, OWNER_USER_ID } from 'officerdb';
 import type { UserRole } from 'officerdb';
 import * as errors from '@@/custom-errors';
+import { OS_USERS_ENABLED } from '@@/os-user';
 
 // Owner-only management of the other accounts. Everything here is gated by ownerGate in
 // users-router.ts; these handlers assume the caller is the Super Admin.
@@ -53,6 +54,9 @@ export const listUsersHandler: Handler = async function (ctx) {
     roles: USER_ROLES,
     assignableRoles: USER_ROLES.filter((r) => r !== 'Super Admin'),
     ownerId: OWNER_USER_ID,
+    // So the UI offers the Linux-account controls only where they can work. On a host without the feature
+    // they would be a button that always reports the same refusal.
+    osUsersEnabled: OS_USERS_ENABLED,
   });
 };