BIOMEKKA 1.8.48 SECRETLESS PORTAL

- Removes personal Wi-Fi, OTA and MQTT credentials from the firmware source.
- Loads credentials from ESP32 NVS Preferences.
- Adds a BioMekka Setup access point when no Wi-Fi credentials exist.
- Enables the setup access point after 90 seconds if the saved network cannot be reached.
- Adds captive-portal routes, Wi-Fi scanning and persistent credential saving.
- Adds /settings for changing Wi-Fi, MQTT and controller/OTA credentials.
- Protects /settings on the normal LAN using HTTP Basic auth with the controller/OTA password.
- Keeps /status, /history, telemetry, MQTT, habitat control and OTA behaviour.

Passwords are not shown back in the web page or /status.

Compile fix:
- Shortened the C++ raw-string delimiter in controller_settings_html.h to stay within the 16-character language limit.