Constructors with long param lists can be hard to reason about when a
number of the args are `None`, in practice. Introducing a struct to use
as the args type helps make things more self-documenting.
### Summary
- Adds an optional SOCKS5 listener via `rama-socks5`
- SOCKS5 is disabled by default and gated by config
- Reuses existing policy enforcement and blocked-request recording
- Blocks SOCKS5 in limited mode to prevent method-policy bypass
- Applies bind clamping to the SOCKS5 listener
### Config
New/used fields under `network_proxy`:
- `enable_socks5`
- `socks_url`
- `enable_socks5_udp`
### Scope
- Changes limited to `codex-rs/network-proxy` (+ `codex-rs/Cargo.lock`)
### Testing
```bash
cd codex-rs
just fmt
cargo test -p codex-network-proxy --offline
