Epic: distribution (Homebrew, Scoop, winget, deb/rpm, Docker image, GitHub Action, install.ps1) #26

Why

Today apic installs via go install, a curl-to-sh script on Linux and macOS, or a manual zip download on Windows. Every comparable tool (Hurl, Bruno's CLI, httpie, task) is one brew install, scoop install or uses: step away. Being a single static binary is apic's headline advantage, so the install story should make that obvious. The course's CI lesson and the README install tabs depend on this epic.

.goreleaser.yaml already builds linux/darwin/windows × amd64/arm64 with cosign signing and SBOMs, so most of this is configuration plus one or two new repositories and secrets.

What is in scope

• P1 Homebrew tap; Docker image on GHCR; a setup-apic GitHub Action in this repo
• P2 Scoop bucket and winget; deb/rpm/apk via nfpm; install.ps1
• P3 mise/aqua/asdf registry entries

Where

• .goreleaser.yaml, .github/workflows/release.yml, install.sh
• Docs: README install section, docs/getting-started.md install tabs, docs/index.md, docs/verifying.md