Add find-me LED locate on master and slaves via ESP-NOW.

UART FIND_ME (client_id 0 = local ring, >0 = unicast), ESPNOW_FIND_ME payload, CLI/dashboard buttons per slave.

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

main/led_ring.h

@@ -5,13 +5,16 @@
 
 /** Default RGB scale (~5 % of full brightness). */
 #define LED_RING_DEFAULT_INTENSITY 13
+/** Full brightness for find-me and similar alerts. */
+#define LED_RING_FULL_INTENSITY 255
 
 typedef enum {
   LED_CMD_CLEAR,
   LED_CMD_SET_DIGIT,
   LED_CMD_SET_COLOR,
   LED_CMD_PROGRESS,
-  LED_CMD_BLINK
+  LED_CMD_BLINK,
+  LED_CMD_FIND_ME
 } led_mode_t;
 
 typedef struct {
@@ -39,4 +42,7 @@ void led_ring_blink_once(uint8_t r, uint8_t g, uint8_t b);
 void led_ring_ota_success(void);
 void led_ring_ota_failed(void);
 
+/** Red / green / blue: 3 blinks each at full intensity. */
+void led_ring_find_me(void);
+
 #endif