Add custom board definition for Heltec WiFi LoRa 32 V3

- Create boards/ directory with custom board JSON for Heltec V3
- Configure platformio.ini to use boards/ directory
- Resolves 'Unknown board ID' error during build

boards/heltec_wifi_lora_32_v3.json

@@ -0,0 +1,32 @@
+{
+  "build": {
+    "core": "esp32",
+    "extra_flags": "-DBOARD_HAS_PSRAM",
+    "f_cpu": "240000000L",
+    "f_flash": "80000000L",
+    "flash_mode": "qio",
+    "mcu": "esp32s3",
+    "variant": "esp32s3"
+  },
+  "connectivity": [
+    "wifi",
+    "ble"
+  ],
+  "debug": {
+    "openocd_board": "esp32s3-board.cfg"
+  },
+  "frameworks": [
+    "arduino",
+    "esp-idf"
+  ],
+  "name": "Heltec WiFi LoRa 32 V3",
+  "upload": {
+    "flash_size": "8MB",
+    "maximum_ram_size": 327680,
+    "maximum_size": 8388608,
+    "require_upload_port": true,
+    "speed": 460800
+  },
+  "url": "https://heltec.org/project/wifi-lora-32-v3/",
+  "vendor": "Heltec"
+}

platformio.ini

@@ -8,6 +8,8 @@ default_envs =
     rak_rak4631
     heltec_v2
 
+boards_dir = boards
+
 extra_configs =
     soc/esp32/platformio.ini
     soc/esp32s3/platformio.ini