Add ArtNetDMX Pico W firmware with dual DMX and docs.

Art-Net to two RS-485 outputs over Wi-Fi (AP or STA with SoftAP fallback), web UI, mDNS, and QLC+/ArtPoll notes for unicast on STA.

Co-authored-by: Cursor <cursoragent@cursor.com>

include/config.h

@@ -0,0 +1,57 @@
+#ifndef CONFIG_H
+#define CONFIG_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include "board.h"
+
+#define CONFIG_MAGIC 0x414E4458u /* 'ANDX' */
+#define CONFIG_VERSION 3
+
+#define CONFIG_SSID_MAX 32
+#define CONFIG_PASS_MAX 64
+#define CONFIG_HOSTNAME_MAX 32
+
+typedef enum {
+    WIFI_MODE_AP = 0,
+    WIFI_MODE_STA = 1,
+    /** Legacy flash value; treated as STA (with AP fallback on failure). */
+    WIFI_MODE_AP_STA = 2,
+} wifi_mode_t;
+
+typedef struct {
+    uint32_t magic;
+    uint32_t version;
+    uint32_t crc;
+    wifi_mode_t wifi_mode;
+    char sta_ssid[CONFIG_SSID_MAX];
+    char sta_pass[CONFIG_PASS_MAX];
+    char ap_ssid[CONFIG_SSID_MAX];
+    char ap_pass[CONFIG_PASS_MAX];
+    uint16_t universe_a;
+    uint16_t universe_b;
+    /* v3: mDNS hostname without ".local" (e.g. "artnetdmx") */
+    char mdns_host[CONFIG_HOSTNAME_MAX];
+} config_t;
+
+void config_set_defaults(config_t *cfg);
+bool config_load(config_t *cfg);
+bool config_save(const config_t *cfg);
+const config_t *config_get(void);
+void config_init(void);
+/** Lowercase DNS-label sanitize into out; returns false if empty/invalid → uses default. */
+bool config_sanitize_hostname(const char *in, char *out, size_t out_sz);
+
+static inline const char *wifi_mode_name(wifi_mode_t m) {
+    switch (m) {
+        case WIFI_MODE_STA:
+        case WIFI_MODE_AP_STA:
+            return "STA";
+        case WIFI_MODE_AP:
+        default:
+            return "AP";
+    }
+}
+
+#endif