feat: add ManagementControllerDriver for server BMCs

A role base for baseboard management controllers (Supermicro, Dell
iDRAC, HPE iLO, Lenovo XCC), reached over Redfish or IPMI, not SSH.

It declares, under TYPE_CHECKING only: get_power_state, set_power_state
(Redfish ResetType actions), get_hardware_inventory (CPUs, DIMMs,
drives, PSUs, NICs, and the server's serial, system UUID and NIC MACs),
get_event_log, get_firmware_inventory and get_management_protocols.

reboot_host restarts the BMC itself (Manager.Reset), never the managed
server, which goes through set_power_state. No HealthMetricsMixin and no
command channel; sensors come through NAPALM's get_environment.

README.md

@@ -36,6 +36,16 @@ class QnapQtsDriver(StorageDriver, HypervisorDriver, LinuxDriver):
 `roles_of(cls)`, `role_keys_of(cls)` and `primary_role_of(cls)` read that back. Nothing
 restates the ranking: there is no precedence table and no attribute to override.
 
+A server's baseboard management controller (Supermicro BMC, Dell iDRAC, HPE iLO,
+Lenovo XCC) is a role of its own, `ManagementControllerDriver` (`management_controller`),
+reached over Redfish or IPMI (`USES_SSH = False`). It is not the server it manages:
+`reboot_host` restarts the BMC (Redfish `Manager.Reset`), while `set_power_state`
+(`On`, `GracefulShutdown`, `ForceOff`, `GracefulRestart`, `ForceRestart`, `PowerCycle`)
+acts on the server. `get_hardware_inventory` carries the server's serial number, system
+UUID and NIC MACs -- what ties the BMC to the host it manages. Its sensors come through
+NAPALM's `get_environment`, with `cpu` and `memory` empty, since a BMC does not know the
+host OS's load; it has no `HealthMetricsMixin` (SNMP) and no command channel.
+
 ### Role bases declare; they never implement
 
 **A role base must not contain a single runtime method — not even a
@@ -258,6 +268,7 @@ Requires Python ≥ 3.10 (tested up to 3.13) and NAPALM ≥ 4.0.
 | `ResidentialGatewayDriver` | Router + firewall + AP in one box | OpenWrt, FritzBox |
 | `PhoneDriver` | IP telephony endpoints | Yealink |
 | `MediaDriver` | Speakers, streamers, media renderers | Sonos, Chromecast |
+| `ManagementControllerDriver` | Server baseboard management controllers | Supermicro BMC, Dell iDRAC, HPE iLO, Lenovo XCC |
 
 Mixins that come with the classes above: `PingSweepMixin` (subnet sweeps, in
 every driver through `DeviceTypeDriver`) and `DhcpServerMixin` (static DHCP