Fix ESP-IDF 5.x firmware compilation for ESP32-S3 build
Port firmware/main to ESP-IDF 5.2 API:
- Add idf_component.yml with mdns and esp_websocket_client managed deps
- Rename esp_ota → app_update, esp_wifi_csi_info_t → wifi_csi_info_t
- Fix freertos/semphr.h include path rename
- Add missing headers: esp_mac.h, esp_netif.h, driver/temperature_sensor.h, string.h, math.h
- Add led.c to SRCS, fix xTaskCreate arg count (7→6)
- Use IDF 5.x temperature_sensor API in place of stub
- Fix mdns_query_ptr signature (add max_results arg)
- Fix url_decode isxdigit unsigned char cast
- Add flash size config (16MB) to sdkconfig.defaults
- Pin managed component versions in dependencies.lock
- Add sdkconfig (generated) to .gitignore
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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