Probe the selected WiFi device with iw to determine which hotspot
protocols it can host: WPA2 requires AP mode; WPA3 requires SAE in AP
mode (SAE_OFFLOAD_AP, or a mac80211 driver with the CMAC cipher for
software SAE). The Raspberry Pi's brcmfmac supports neither, so Pis
correctly offer WPA2 only (verified against real Pi 4/Pi 5 iw output).
The protocol is saved as hotspot.protocol in controller.yaml.
enable_hotspot() now always sets the Hotspot connection's key-mgmt
explicitly (sae + required PMF for WPA3) so a reused profile cannot
keep a stale protocol, and reverts to WPA2 if the driver rejects SAE.
New GET /api/hotspot/protocols endpoint; protocol dropdowns added to
both the ControllerPage React UI and the fallback controller UI.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>