install-latest.sh fails on GitHub API rate limits from shared/datacenter IPs

[myurasov-nv]

Problem

bin/install-latest.sh resolves the latest release via unauthenticated GitHub API calls; from shared/datacenter egress IPs the quota is exhausted (same root cause as #411) and the install fails:

API rate limit exceeded ... set GITHUB_TOKEN to avoid rate limits

Observed on a datacenter Ubuntu host, 2026-07-25.

Fix

• On API failure, fall back to the API-free redirect: https://github.com/brevdev/brev-cli/releases/latest/download/<asset>
• Keep GITHUB_TOKEN optional (mirrors the fix: authenticate GitHub API calls to avoid 60/hr unauthenticated rate limit #411 fix for CLI-internal calls)

Workaround

1. On any authenticated machine: gh api repos/brevdev/brev-cli/releases/latest -> asset URL
2. On the target: curl -fsSL -o /tmp/brev.tgz <url> && tar -xzf /tmp/brev.tgz -C /tmp && sudo mv /tmp/brev /usr/local/bin/