forge_admin() spawned nixos-container run hive-forge directly from the
hive-core process. nixos-container run uses nsenter to enter the container
namespaces, which requires root. hive-core is unprivileged, so every call
failed with: nsenter: stat of /proc/<pid>/ns/user failed: Permission denied
Fix: add RunForgeAdmin { args } to PrivRequest. hive-priv (root) handles
it by spawning nixos-container run hive-forge -- runuser -u forgejo --
forgejo --work-path /var/lib/forgejo admin <args>. forge_admin() now calls
priv_client::run_forge_admin().
matrix: ensure_user_for hit M_USER_IN_USE then failed when the stored
password file was missing (state dirs wiped but homeserver kept accounts).
Previously required manual hivectl matrix reset-password <name>.
Fix: add auto_reset_password() — calls the admin API (PUT
/_synapse/admin/v2/users/@<name>:<server> with the hive admin token) to
set a new random password, then proceeds with login. Falls back to the
existing manual-recovery error if the admin token is unavailable.
Closes#1234
34bc4c0b06