Feature: Add 'openfang update' self-update command

[ntamero]

Feature Request

OpenFang currently has no built-in update command. Users must manually download the latest release from GitHub, stop the daemon, replace the binary, and restart.

Desired Behavior

openfang update          # Check and update to latest version
openfang update --check  # Only check if update available

The command should:

1. Check GitHub releases for the latest version
2. Compare with current version (openfang --version)
3. Download the correct binary for the platform
4. Verify SHA256 checksum
5. Gracefully stop the daemon
6. Replace the binary
7. Restart the daemon
8. Confirm the update was successful

Current Workaround

Manual process via SSH:

curl -L -o /tmp/openfang.tar.gz https://github.com/RightNow-AI/openfang/releases/latest/download/openfang-x86_64-unknown-linux-gnu.tar.gz
tar xzf /tmp/openfang.tar.gz -C /tmp
openfang stop
cp /tmp/openfang /root/.openfang/bin/openfang
openfang start

Additional Suggestions

• openfang cron could schedule auto-update checks (e.g., every 6 hours)
• Dashboard notification when a new version is available
• Rollback option if update fails

Environment

• OpenFang v0.3.2