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/login/Cargo.toml

@@ -7,10 +7,12 @@ version = { workspace = true }
 workspace = true
 
 [dependencies]
+base64 = "0.22"
 chrono = { version = "0.4", features = ["serde"] }
 reqwest = { version = "0.12", features = ["json"] }
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
+thiserror = "2.0.12"
 tokio = { version = "1", features = [
     "io-std",
     "macros",
@@ -20,4 +22,5 @@ tokio = { version = "1", features = [
 ] }
 
 [dev-dependencies]
+pretty_assertions = "1.4.1"
 tempfile = "3"