fw: robust HTTP body reads, CORS preflight, LED off at boot; update docs

- app_net.c: replace bare httpd_req_recv with recv_body_capped/alloc
  helpers (TCP-safe, full-body reads); add OPTIONS/* CORS preflight
  handler; bump WS broadcast buffer to 2048; add CORS Allow-Methods
- CMakeLists (net_service): add http_parser dep for HTTP_OPTIONS
- nfc_engine/pn532_core: add nfc_access_lock/unlock mutex, board-RGB
  quiet helper, UL type detection, general-status improvements
- pn532_transport: minor cleanup
- main.c: call board_rgb_led_quiet() at boot to kill onboard LED
- sdkconfig.defaults: add board RGB Kconfig defaults
- README, docs/LIMITATIONS, docs/PINOUT: expand and correct

Made-with: Cursor

firmware/components/nfc_engine/include/nfc_engine/nfc_engine.h

@@ -32,6 +32,9 @@ esp_err_t nfc_poll_passive_target(nfc_tag_info_t *out);
 bool nfc_tag_is_mifare_classic(const nfc_tag_info_t *tag);
 bool nfc_tag_is_mifare_classic_4k(const nfc_tag_info_t *tag);
 bool nfc_tag_is_type2(const nfc_tag_info_t *tag);
+int nfc_mifare_sector_count(const nfc_tag_info_t *tag);
+bool nfc_mifare_sector_layout(const nfc_tag_info_t *tag, int sector, int *first_block, int *num_blocks,
+                              uint8_t *trailer_block);
 
 esp_err_t nfc_mifare_authenticate_block(const nfc_tag_info_t *tag, uint8_t block_no,
                                         const nfc_mifare_key_t *key);
@@ -42,6 +45,7 @@ esp_err_t nfc_ultralight_read_page(uint8_t page, uint8_t data[4]);
 esp_err_t nfc_ultralight_write_page(uint8_t page, const uint8_t data[4]);
 
 esp_err_t nfc_ul_fast_read(uint8_t start_page, uint8_t *out, size_t out_max, size_t *got);
+esp_err_t nfc_type2_get_version(uint8_t version[8]);
 
 /** Build JSON snapshot of last seen tag + optional blocks (caller frees cJSON). */
 cJSON *nfc_tag_to_json(const nfc_tag_info_t *tag);