collab: Add traces for user LLM rate limits (#16610)

This PR adds traces for when users hit LLM rate limits.

We were already emitting telemetry events for these to Clickhouse, but
it will be handy to have them available in Axiom as well.

Release Notes:

- N/A

crates/collab/src/llm.rs

@@ -463,6 +463,24 @@ async fn check_usage_limit(
             };
 
             if let Some(client) = state.clickhouse_client.as_ref() {
+                tracing::info!(
+                    target: "user rate limit",
+                    user_id = claims.user_id,
+                    login = claims.github_user_login,
+                    authn.jti = claims.jti,
+                    is_staff = claims.is_staff,
+                    provider = provider.to_string(),
+                    model = model.name,
+                    requests_this_minute = usage.requests_this_minute,
+                    tokens_this_minute = usage.tokens_this_minute,
+                    tokens_this_day = usage.tokens_this_day,
+                    users_in_recent_minutes = users_in_recent_minutes,
+                    users_in_recent_days = users_in_recent_days,
+                    max_requests_per_minute = per_user_max_requests_per_minute,
+                    max_tokens_per_minute = per_user_max_tokens_per_minute,
+                    max_tokens_per_day = per_user_max_tokens_per_day,
+                );
+
                 report_llm_rate_limit(
                     client,
                     LlmRateLimitEventRow {