Add ESPectre WiFi CSI Motion Detection

ESPectre is a motion detection system based on WiFi spectrum analysis (CSI).
Supports ESP32-C6, ESP32-S3, ESP32-C3 and other ESP32 variants.

Features:
- Privacy-preserving (no cameras/audio)
- Through-wall detection
- Auto-calibration
- Adjustable sensitivity via Home Assistant

Author: francescopace

src/docs/devices/ESPectre/espectre-ha.png

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+---
+title: ESPectre - WiFi CSI Motion Detection
+date-published: 2024-12-10
+type: sensor
+standard: global
+board: esp32
+difficulty: 1
+made-for-esphome: true
+project-url: https://github.com/francescopace/espectre
+---
+
+## Description
+
+ESPectre is a motion detection system based on **WiFi spectrum analysis** with native Home Assistant integration via ESPHome.
+
+Unlike traditional PIR sensors, ESPectre detects movement by analyzing changes in WiFi signals.
+No cameras, no microphones, no wearables required.
+
+### Features
+
+- **WiFi-based detection**: Uses CSI (Channel State Information) from existing WiFi signals
+- **Privacy-preserving**: No cameras, no audio, no identifying data
+- **Through-wall detection**: WiFi signals penetrate walls and obstacles
+- **Auto-calibration**: Automatically selects optimal subcarriers
+- **Adjustable sensitivity**: Threshold control from Home Assistant
+- **Multiple platforms**: ESP32-C6, ESP32-S3, ESP32-C3, ESP32-C5, ESP32-S2, ESP32
+
+### Entities Created
+
+- **binary_sensor.espectre_motion_detected** - Motion state (on/off)
+- **sensor.espectre_movement_score** - Movement intensity value
+- **number.espectre_threshold** - Detection threshold (adjustable)
+
+## Supported Hardware
+
+| Platform | Status | WiFi |
+|----------|--------|------|
+| ESP32-C6 | ✅ Tested | WiFi 6 |
+| ESP32-S3 | ✅ Tested | WiFi 4 |
+| ESP32-C3 | ✅ Tested | WiFi 4 |
+| ESP32-C5 | ⚠️ Experimental | WiFi 6 |
+| ESP32-S2 | ⚠️ Experimental | WiFi 4 |
+| ESP32 | ⚠️ Experimental | WiFi 4 |
+
+## Setup
+
+1. Flash the device using ESPHome Dashboard or CLI
+2. Configure WiFi via:
+   - **BLE**: ESPHome app or Home Assistant Companion
+   - **USB**: [web.esphome.io](https://web.esphome.io)
+   - **Captive Portal**: Connect to "ESPectre Fallback" AP
+3. Device auto-discovers in Home Assistant
+
+## Configuration
+
+Download the example configuration for your platform from [GitHub](https://github.com/francescopace/espectre/tree/main/examples).
+
+```yaml
+external_components:
+  - source:
+      type: git
+      url: https://github.com/francescopace/espectre
+      ref: main
+    components: [ espectre ]
+
+espectre:
+  id: espectre_csi
+  # Optional parameters:
+  # segmentation_threshold: 1.0    # Motion sensitivity (0.5-10.0)
+  # traffic_generator_rate: 100    # CSI packets/sec (0-1000)
+```
+
+![ESPectre HA](espectre-ha.png "ESPectre - Home Assistant Dashboard")
+
+## Important Notes
+
+- **Calibration**: Keep room still for 10 seconds after boot
+- **Traffic Generator**: Required for CSI packet generation (enabled by default)
+- **Optimal Distance**: 3-8 meters from WiFi router
+
+## Support
+
+- [Documentation](https://github.com/francescopace/espectre#readme)
+- [Setup Guide](https://github.com/francescopace/espectre/blob/main/SETUP.md)
+- [Tuning Guide](https://github.com/francescopace/espectre/blob/main/TUNING.md)
+- [GitHub Issues](https://github.com/francescopace/espectre/issues)
+- [Discussions](https://github.com/francescopace/espectre/discussions)
+
+![ESPectre lab](espectre-lab.jpg "ESPectre - Home lab")