README missing documentation for PORT, HOST, and RECLIP_NO_UPDATE environment variables #67

The app.py supports three environment variables for configuration:

• PORT: server port, defaults to 8899
• HOST: bind address, defaults to 127.0.0.1
• RECLIP_NO_UPDATE: set to 1 to skip yt-dlp update on startup (used in reclip.sh)

None of these are documented in the README.

Location

README.md, under or after the Quick Start section.

Why it matters

1. Users who want to run ReClip on a different port or bind to 0.0.0.0 (e.g. in a Docker context or on a remote server) have to read the source code to discover the HOST variable.
2. The RECLIP_NO_UPDATE flag is useful for users who prefer to manage yt-dlp versions manually or run in offline environments, but it is only visible in the shell script.
3. In the Docker path, the Dockerfile CMD hardcodes gunicorn -b 0.0.0.0:8899, which means the PORT and HOST environment variables are silently ignored when running the Docker image. This inconsistency should at least be mentioned.

Suggested improvement

Add a small "Configuration" section to the README listing these three variables with their defaults and descriptions.