Release archives should include `ap-proxy` (relay server) alongside `aac`

## Context

The `v0.11.0` GitHub Release assets (`aac-linux-x86_64.tar.gz`, etc.) only ship the `aac` CLI binary. The `ap-proxy` relay server binary is built from source at that tag but is **not** included in the release archives.

## Request

Please also package and distribute the `ap-proxy` relay server binary in future release archives. The relay server has real value for self-hosting users who want to run their own Agent Access relay rather than relying on the default `ap.lesspassword.dev` server.

## Why it matters

Downstream packagers (Arch Linux AUR, etc.) currently have two choices:

1. **Use the upstream release archive** — simple, but only the `aac` client CLI is available. Users who want to self-host a relay must build from source manually.
2. **Build from source** — allows the package to include both `aac` and `ap-proxy`, but requires pulling in the full Rust toolchain as a build dependency and significantly increases package build time.

The first path is the one upstream clearly prefers (it's what the installation docs recommend), but it silently omits a useful binary that exists in the workspace.

## Suggested change

Add `ap-proxy` (or `ap-relay`, post-rename) to the CI release workflow so it is archived alongside `aac` in the platform-specific release tarballs.

## Related

- `ap-proxy` was renamed to `ap-relay` in PR #133 (commit 29db468) and will ship under that name in v0.12.0+. The same request applies regardless of the binary name.
- For reference, the Arch Linux AUR package `bitwarden-agent-access` builds from source specifically to include both binaries.