ESP32-C3 already uses the QEMU backend via Esp32Bridge, not browser-side
emulation. This adds MicroPython support by including C3 in the supported
set, adding the C3 firmware variant to the loader, and bundling the
fallback firmware binary.
Also fixes misleading type comments that said "browser emulation" for C3
boards — they actually use QEMU backend.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
David Montero Crespo