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.

.gitignore

@@ -0,0 +1,5 @@
+/dist/
+/passv
+*.out
+*.test
+.env