Add CodexHttpClient wrapper with request logging (#5564)

## Summary
- wrap the default reqwest::Client inside a new
CodexHttpClient/CodexRequestBuilder pair and log the HTTP method, URL,
and status for each request
- update the auth/model/provider plumbing to use the new builder helpers
so headers and bearer auth continue to be applied consistently
- add the shared `http` dependency that backs the header conversion
helpers

## Testing
- `CODEX_SANDBOX=seatbelt CODEX_SANDBOX_NETWORK_DISABLED=1 cargo test -p
codex-core`
- `CODEX_SANDBOX=seatbelt CODEX_SANDBOX_NETWORK_DISABLED=1 cargo test -p
codex-chatgpt`
- `CODEX_SANDBOX=seatbelt CODEX_SANDBOX_NETWORK_DISABLED=1 cargo test -p
codex-tui`

------
https://chatgpt.com/codex/tasks/task_i_68fa5038c17483208b1148661c5873be

codex-rs/core/src/chat_completions.rs

@@ -4,6 +4,7 @@ use crate::ModelProviderInfo;
 use crate::client_common::Prompt;
 use crate::client_common::ResponseEvent;
 use crate::client_common::ResponseStream;
+use crate::default_client::CodexHttpClient;
 use crate::error::CodexErr;
 use crate::error::ConnectionFailedError;
 use crate::error::ResponseStreamFailed;
@@ -36,7 +37,7 @@ use tracing::trace;
 pub(crate) async fn stream_chat_completions(
     prompt: &Prompt,
     model_family: &ModelFamily,
-    client: &reqwest::Client,
+    client: &CodexHttpClient,
     provider: &ModelProviderInfo,
     otel_event_manager: &OtelEventManager,
 ) -> Result<ResponseStream> {