Add RF tracker web UI and FastAPI reader

Introduce a new dev-utils/rf-tracker tool that visualizes and serves RF antenna data from a Rocket M2 device.

Files added:
- index.html: standalone web UI with a directional display, calibration controls (bias), smoothing, and a normalized strength meter that polls /signal.
- main.py: FastAPI app serving the UI and a /signal endpoint that queries the Rocket device and returns chain0/chain1, error, normalized, and strength values. Host/user/password can be configured via ROCKET_HOST/ROCKET_USER/ROCKET_PASS env vars.
- rocket_reader.py: SSH reader using paramiko to run mca-status, parse chain values, compute error/strength, and normalize error.
- requirements.txt: declares fastapi, uvicorn, and paramiko.

Purpose: provide a lightweight local web tool to point/align an antenna by reading per-chain RSS values from the Rocket device and showing direction, strength, and calibration controls.

Author: haoruizhou