Document audit logging tracing ID support (v1.18.0) (#2287)

* Document audit logging tracing ID support (v1.18.0)

Add a "Tracing IDs" subsection to the Audit Logging section of security.md,
and code snippets for all six client SDKs showing how to attach an
x-request-id header to requests so it appears in audit log entries.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Small edits

* Don't hide imports in Python snippet

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

qdrant-landing/content/documentation/headless/snippets/audit-tracing-id/simple/rust.rs

@@ -0,0 +1,12 @@
+use qdrant_client::Qdrant;
+
+pub async fn main() -> anyhow::Result<()> {
+    let client = Qdrant::from_url("http://localhost:6334").build()?; // @hide
+
+    client
+        .with_header("x-request-id", "my-trace-id")
+        .list_collections()
+        .await?;
+
+    Ok(())
+}