install a new node in the gnt-fsn cluster (fsn-node-03)

we decided to use the part of the emergency budget allocated to a new Ganeti node to create such a node now. if we follow the current order, the new node would be named fsn-node-03.

our new FSN Ganeti cluster (gnt-fsn) is full. when it reboots, the load goes through the roof and it can barely keep up when one node is missing.

plus we need extra capacity to cover the various decommissioning process we have under way (#32802 (moved), #31686 (moved), #29974 (moved)). it's now essential to have that extra capacity to cover for those retirements.

the retirement of the kvm* boxes, in particular, might give us the extra budget required to pop another node (which would be fsn-node-04, but let's not get ahead of ourselves).