Add firmware binary release assets after provisioning support

[sensmonitor]

Goal

Prepare optional firmware binary assets for future releases.

Blocked by

• Runtime APN/device provisioning.
• Clear hardware-specific build profiles.
• Documentation for flashing and configuration.

Candidate assets

• LilyGO T-SIM7000G firmware binary.
• Generic ESP32 UART modem firmware binary, if configuration is safe.

Notes

Do not publish binaries until users can configure device/operator settings safely.