The admin bootstrap password was printed once, as one line among roughly
45 fx lines, and under docker run -d went to container logs subject to
rotation. There was no reset path at all -- no subcommand, no forgot-password
flow, no env override -- so recovery meant hand-deleting the users row from
webhooker.db, which was documented nowhere.
Adds webhooker resetpw [-generate] <username>. The password is read from
stdin or generated with the existing crypto/rand helper, never taken from
argv where /proc would publish it. It reuses the existing Argon2id hashing
rather than reimplementing the parameters, and writes a single UPDATE only
after the hash is complete, so no failure can leave an account with no
usable password. An unknown username is a hard error and never creates an
account.
It refuses to run against a DATA_DIR held by a live instance, via the
exclusive lock from #201. DATA_DIR and webhooker.db are checked to exist
before the lock is acquired, so a mistyped path creates nothing -- neither
a directory tree nor a stray lock file.
The bootstrap password now appears exactly once, in a distinct banner
written straight to a caller-named writer rather than as an fx log line.
