feat: parse info from auth.json and show in /status (#1923)

- `/status` renders
    ```
    signed in with chatgpt
      login: example@example.com
      plan: plus
    ```
- Setup for using this info in a few more places.

---------

Co-authored-by: Michael Bolin <mbolin@openai.com>

codex-rs/Cargo.lock

@@ -792,11 +792,14 @@ dependencies = [
 name = "codex-login"
 version = "0.0.0"
 dependencies = [
+ "base64 0.22.1",
  "chrono",
+ "pretty_assertions",
  "reqwest",
  "serde",
  "serde_json",
  "tempfile",
+ "thiserror 2.0.12",
  "tokio",
 ]