Initial commit — firmware WireClaw ESP32-S3 fonctionnel

- Heartbeat MAVLink v1 toutes les 1s (broadcast 192.168.4.255:14553)
- Relais WiFi <-> UART (Jetson <-> Pi Zero) sur ports 14550-14553
- LED RGB WS2812 GPIO48 : rouge pulsé (attente), vert dim (idle), flash vert (heartbeat)
- MODE_AP=true : hotspot WireClaw-CAM / false : connexion Jetson
- Fix: retrait ARDUINO_USB_CDC_ON_BOOT (carte Freenove utilise CH343/UART0)

include/README

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+
+This directory is intended for project header files.
+
+A header file is a file containing C declarations and macro definitions
+to be shared between several project source files. You request the use of a
+header file in your project source file (C, C++, etc) located in `src` folder
+by including it, with the C preprocessing directive `#include'.
+
+```src/main.c
+
+#include "header.h"
+
+int main (void)
+{
+ ...
+}
+```
+
+Including a header file produces the same results as copying the header file
+into each source file that needs it. Such copying would be time-consuming
+and error-prone. With a header file, the related declarations appear
+in only one place. If they need to be changed, they can be changed in one
+place, and programs that include the header file will automatically use the
+new version when next recompiled. The header file eliminates the labor of
+finding and changing all the copies as well as the risk that a failure to
+find one copy will result in inconsistencies within a program.
+
+In C, the convention is to give header files names that end with `.h'.
+
+Read more about using header files in official GCC documentation:
+
+* Include Syntax
+* Include Operation
+* Once-Only Headers
+* Computed Includes
+
+https://gcc.gnu.org/onlinedocs/cpp/Header-Files.html

include/mavlink_heartbeat.h

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+#pragma once
+#include <stdint.h>
+
+// ─────────────────────────────────────────────────────────────
+// MAVLink v1 — HEARTBEAT (msg_id = 0)
+// Trame complète : 17 octets
+//
+//  Byte  Field
+//  0     STX       0xFE (MAVLink v1 magic)
+//  1     LEN       9    (payload = 9 octets)
+//  2     SEQ       séquence incrémentale
+//  3     SYS_ID    system id (on se déclare comme GCS = 255)
+//  4     COMP_ID   component id (GCS = 0)
+//  5     MSG_ID    0 (HEARTBEAT)
+//  6-14  PAYLOAD   9 octets (voir ci-dessous)
+//  15-16 CRC       CRC-16/MCRF4XX avec CRC_EXTRA = 50
+//
+// Payload HEARTBEAT (9 octets, little-endian) :
+//  [0-3] custom_mode        uint32  0x00000000
+//  [4]   type               uint8   MAV_TYPE_GCS = 6
+//  [5]   autopilot          uint8   MAV_AUTOPILOT_INVALID = 8
+//  [6]   base_mode          uint8   0
+//  [7]   system_status      uint8   MAV_STATE_ACTIVE = 4
+//  [8]   mavlink_version    uint8   3
+// ─────────────────────────────────────────────────────────────
+
+// CRC-16/MCRF4XX (algorithme MAVLink)
+static inline void mavCrcAccumulate(uint8_t data, uint16_t &crc) {
+    uint8_t tmp = data ^ (uint8_t)(crc & 0xFF);
+    tmp ^= (tmp << 4);
+    crc = (crc >> 8) ^ ((uint16_t)tmp << 8) ^ ((uint16_t)tmp << 3) ^ ((uint16_t)tmp >> 4);
+}
+
+// Construit un paquet HEARTBEAT MAVLink v1 dans buf (doit faire >= 17 octets)
+// Retourne la taille du paquet (toujours 17)
+static inline uint8_t mavlinkBuildHeartbeat(uint8_t *buf, uint8_t &seq) {
+    const uint8_t PAYLOAD_LEN  = 9;
+    const uint8_t SYS_ID       = 255;  // GCS
+    const uint8_t COMP_ID      = 0;    // GCS component
+    const uint8_t MSG_ID       = 0;    // HEARTBEAT
+    const uint8_t CRC_EXTRA    = 50;   // valeur fixe MAVLink pour msg #0
+
+    // Header
+    buf[0] = 0xFE;          // STX
+    buf[1] = PAYLOAD_LEN;
+    buf[2] = seq++;         // numéro de séquence (overflow géré par uint8_t)
+    buf[3] = SYS_ID;
+    buf[4] = COMP_ID;
+    buf[5] = MSG_ID;
+
+    // Payload (little-endian)
+    buf[6]  = 0x00;  // custom_mode [0]
+    buf[7]  = 0x00;  // custom_mode [1]
+    buf[8]  = 0x00;  // custom_mode [2]
+    buf[9]  = 0x00;  // custom_mode [3]
+    buf[10] = 6;     // type = MAV_TYPE_GCS
+    buf[11] = 8;     // autopilot = MAV_AUTOPILOT_INVALID
+    buf[12] = 0;     // base_mode
+    buf[13] = 4;     // system_status = MAV_STATE_ACTIVE
+    buf[14] = 3;     // mavlink_version
+
+    // CRC sur header (sans STX) + payload + CRC_EXTRA
+    uint16_t crc = 0xFFFF;
+    for (uint8_t i = 1; i <= 5 + PAYLOAD_LEN; i++) {
+        mavCrcAccumulate(buf[i], crc);
+    }
+    mavCrcAccumulate(CRC_EXTRA, crc);
+
+    buf[15] = crc & 0xFF;         // CRC low byte
+    buf[16] = (crc >> 8) & 0xFF;  // CRC high byte
+
+    return 17;
+}