Replace psutil.net_if_addrs() scan with a deterministic name derived from
the switch's node UUID: gns3 + first 6 hex chars (10 chars, fits kernel
IFNAMSIZ limit of 15). Taps: <bridge>-<port> (12-13 chars).
Crash recovery: brctl delete the bridge first (best-effort), then create
fresh. Stale bridges from abnormal gns3server shutdown are automatically
reclaimed on the next start — no EEXIST or leaked interfaces.
Remove _free_iface helper and psutil import (no longer needed).
18a123e0b9