build(cli): scoop bucket for ferrvault CLI (Windows)

[BryanFRD]

Goal

`scoop install ferrvault` works for Windows users (or via our own bucket, `scoop bucket add ferrlabs https://github.com/FerrLabs/scoop-bucket && scoop install ferrvault`).

Why

Today Windows users have to download the zip from GitHub Releases and add to PATH manually. Scoop is the de-facto Windows-CLI package manager.

What to do

1. Create a public repo `FerrLabs/scoop-bucket`.
2. Add `bucket/ferrvault.json`:

{
  "version": "0.1.1",
  "description": "Consumer CLI for FerrVault — fetch and inject secrets",
  "homepage": "https://ferrvault.com",
  "license": "MPL-2.0",
  "architecture": {
    "64bit": {
      "url": "https://github.com/FerrLabs/FerrVault/releases/download/cli-v0.1.1/ferrvault-windows-amd64.zip",
      "hash": "<sha256>"
    }
  },
  "bin": "ferrvault.exe",
  "checkver": {
    "github": "https://github.com/FerrLabs/FerrVault",
    "regex": "tag/cli-v([\\d.]+)"
  },
  "autoupdate": {
    "architecture": {
      "64bit": {
        "url": "https://github.com/FerrLabs/FerrVault/releases/download/cli-v$version/ferrvault-windows-amd64.zip"
      }
    },
    "hash": {
      "url": "$url.sha256"
    }
  }
}

3. Add a release-time job to bump `bucket/ferrvault.json` on every `cli-v*` push (scoop `autoupdate` handles version detection from the JSON, but we need to commit the version bump for users who don't have autoupdate enabled).