Add passv: a Vault-backed drop-in for pass

Provide a password-store CLI that keeps pass's on-disk layout (<name>.gpg
binary OpenPGP under $PASSWORD_STORE_DIR) but routes all encryption and
decryption through a vault-plugin-secrets-gpg engine mount, so the GPG private
key never lives on the client.

- Implement init/show/ls/insert/generate/edit/rm/mv/cp/find/grep/git with
  pass-compatible flags and implicit `passv <name>`=show dispatch.
- Resolve the recipient from a Vault ref: .gpg-id holds <mount>/<key> for
  passv-native stores, or a sibling .vault-id lets a store keep real GPG
  fingerprints in .gpg-id for dual gpg+Vault use.
- mv/cp re-encrypt across differing recipients; same-recipient moves copy the
  ciphertext verbatim.
- Ship the sibling build/packaging/CI: nfpm RPM to /usr/bin/passv (artifactapi
  rpm-internal on v* tag), Woodpecker PR/release pipelines, unit tests plus a
  real-Vault e2e that also proves dual gpg+Vault decryption.
- README covers store creation, migrating a GPG pass store, and dual-mode.

scripts/build-rpm.sh

@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+#
+# Package the (already built) passv binary into an RPM with nfpm.
+# Usage: scripts/build-rpm.sh [version]   (version defaults to $CI_COMMIT_TAG)
+#
+set -euo pipefail
+
+ROOT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+cd "${ROOT_DIR}"
+
+VERSION="${1:-${CI_COMMIT_TAG:-0.0.0-dev}}"
+VERSION="${VERSION#v}"
+DIST="dist"
+
+if [ ! -f "${DIST}/passv" ]; then
+  echo "ERROR: ${DIST}/passv not found; run 'make build' first" >&2
+  exit 1
+fi
+
+export PACKAGE_VERSION="${VERSION}"
+export PACKAGE_RELEASE="1"
+export PACKAGE_ARCH="amd64"
+export PACKAGE_PLATFORM="linux"
+export PACKAGE_MAINTAINER="Ben Vincent <ben@unkin.net>"
+export PACKAGE_HOMEPAGE="https://git.unkin.net/unkin/passv"
+export PACKAGE_LICENSE="MIT"
+
+envsubst < packaging/nfpm.yaml > "${DIST}/nfpm.yaml"
+nfpm pkg --config "${DIST}/nfpm.yaml" --target "${DIST}" --packager rpm
+
+echo "Built:"
+ls -1 "${DIST}"/*.rpm