Upstream uses non-standard OS/arch names (x64, ia32, win32, arm) and
ships both bare binaries and .gz-compressed copies. classifyFFmpegDist
maps those to canonical names and keeps only bare binaries.
Also adds source-override logic to installerconf so that
github_releases + source = ffmpegdist works: GitHub is used for
fetching while the custom classifier handles classification.
Replaces the inline &http.Client{Timeout: 30s} with httpclient.New(),
which enforces TLS 1.2+, per-level timeouts, no HTTPS→HTTP redirect
downgrade, connection pooling, and automatic retry with backoff.
The delayTransport (page-delay flag) now wraps httpclient's transport
instead of http.DefaultTransport, preserving all security properties.
Rewrites the Node.js release classification pipeline in Go. webicached
fetches upstream releases (GitHub, Gitea, GitLab, HashiCorp, custom
sources), classifies assets by OS/arch/variant, and writes legacy-format
JSON caches compatible with the existing webinstall.dev API.
Git-clone packages emit git_tag and git_commit_hash from real repo
clones — no fabricated refs.
