feat: Add baseline calibration & presence detection (v1.7)

CALIBRATE command captures per-subcarrier CSI amplitudes over a timed
window and stores the averaged baseline in NVS. PRESENCE command enables
real-time scoring via normalized Euclidean distance against the baseline,
with rolling window averaging and 10s holdoff on state transitions.

New commands: CALIBRATE [3-60|STATUS|CLEAR], PRESENCE [ON|OFF|THRESHOLD]
New NVS keys: bl_amps (blob), bl_nsub, presence, pr_thresh
New STATUS fields: presence=, pr_score=
New events: calibrate=done, presence=0|1

ROADMAP.md

@@ -120,6 +120,19 @@ Note: Promiscuous mode (probe/deauth capture) disabled on original ESP32 — bre
 - [ ] Deep sleep mode with wake-on-CSI-motion
 - [ ] Battery-optimized duty cycling
 
+## v1.7 - Baseline Calibration & Presence Detection [DONE]
+- [x] CALIBRATE command (capture N seconds of CSI with room empty, average per-subcarrier amplitudes, store in NVS)
+- [x] CALIBRATE STATUS / CALIBRATE CLEAR subcommands
+- [x] Presence scoring (normalized Euclidean distance of live CSI vs baseline, rolling window)
+- [x] PRESENCE ON/OFF command (NVS persisted, requires valid baseline)
+- [x] PRESENCE THRESHOLD command (tunable 0.001-1.0, NVS persisted)
+- [x] Presence events (`EVENT,<hostname>,presence=<0|1> score=<float>`) with 10s holdoff
+- [x] Calibration done event (`EVENT,<hostname>,calibrate=done packets=<n> nsub=<n>`)
+- [x] presence= and pr_score= fields in STATUS reply
+- [x] NVS persistence for baseline (bl_amps blob, bl_nsub) and presence config
+- [ ] Tune presence threshold per room with real-world testing
+- [ ] Pi-side presence event handling in watch daemon
+
 ## v2.0 - Hardware Upgrade (ESP32-S3/C6)
 
 Requires replacing current ESP32 (original) DevKitC V1 boards with ESP32-S3