The replica-placement rule (data-center/rack/same-node limits plus host
anti-affinity) existed three times: the shell's satisfyReplicaPlacement/isGoodMove
used by volume.balance, fix.replication, and tier.move, and a line-for-line port
in the maintenance balance worker. Move the canonical logic into
weed/topology/balancer on a shared Location type; the shell and worker keep thin
adapters that convert their own location representation and call it. Behavior is
unchanged (the shared IsGoodMove keeps the shell's reject-move-to-self guard, and
all four replica test suites pass).
Chris Lu
d02ee6d5df