fix(firmware): accept WPA/WPA2-mixed routers; warn about compact-board thermal risk

Lower the STA auth threshold from WPA2_PSK to WPA_PSK so routers running
WPA/WPA2-mixed compatibility mode aren't rejected with
WIFI_REASON_NO_AP_FOUND_IN_AUTHMODE_THRESHOLD (reason=211), and log the
disconnect reason/rssi instead of retrying blind. Also document the thermal
risk of running this firmware's continuous-radio, tier-2 DSP pipeline on
coin-sized clone boards (ESP32-S3-Zero, SuperMini) with minimal PCB copper
and budget regulators, after a field report of three such boards failing to
power on following a normal session.

Co-Authored-By: claude-flow <ruv@ruv.net>

firmware/esp32-csi-node/README.md

@@ -113,6 +113,8 @@ curl http://<ESP32_IP>:8032/wasm/list
 
 > **Tip:** A single node provides presence and vital signs along its line of sight. Multiple nodes (3-6) create a multistatic mesh that resolves 3D pose with <30 mm jitter and zero identity swaps.
 
+> **⚠️ Thermal warning — compact boards (ESP32-S3-Zero, SuperMini, other coin-sized clones):** This firmware runs the WiFi radio with modem sleep disabled (`WIFI_PS_NONE`, required for continuous CSI capture) plus a full edge-processing DSP pipeline on Core 1 (`edge_tier=2`) plus, on ADR-183 builds, a continuous 40 Hz onboard LED driver. That's sustained high current draw with no duty-cycling. Full-size dev boards (DevKitC-1, XIAO) have more copper pour and thermal mass around the regulator and tolerate this fine. Coin-sized clones with minimal PCB area and budget regulators may run hot to the touch during normal operation, and in at least one field report, boards that ran hot during a session failed to power on afterward (regulator damage suspected — see issue tracker). Give these boards airflow, don't stack or enclose them, and check them by touch during the first several minutes of a new deployment. If a board is uncomfortably hot (not just warm), power it down and let it cool before continuing.
+
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 ## Firmware Architecture