chore: move src/llama_stack/ui to src/llama_stack_ui (#4068)

# What does this PR do?
This better separates UI from backend code, which was a point of
confusion often for our beloved AI friends.


## Test Plan
CI

src/llama_stack_ui/app/logs/chat-completions/[id]/page.tsx

@@ -0,0 +1,59 @@
+"use client";
+
+import { useEffect, useState } from "react";
+import { useParams } from "next/navigation";
+import { ChatCompletion } from "@/lib/types";
+import { ChatCompletionDetailView } from "@/components/chat-completions/chat-completion-detail";
+import { useAuthClient } from "@/hooks/use-auth-client";
+
+export default function ChatCompletionDetailPage() {
+  const params = useParams();
+  const id = params.id as string;
+  const client = useAuthClient();
+
+  const [completionDetail, setCompletionDetail] =
+    useState<ChatCompletion | null>(null);
+  const [isLoading, setIsLoading] = useState<boolean>(true);
+  const [error, setError] = useState<Error | null>(null);
+
+  useEffect(() => {
+    if (!id) {
+      setError(new Error("Completion ID is missing."));
+      setIsLoading(false);
+      return;
+    }
+
+    const fetchCompletionDetail = async () => {
+      setIsLoading(true);
+      setError(null);
+      setCompletionDetail(null);
+      try {
+        const response = await client.chat.completions.retrieve(id);
+        setCompletionDetail(response as ChatCompletion);
+      } catch (err) {
+        console.error(
+          `Error fetching chat completion detail for ID ${id}:`,
+          err
+        );
+        setError(
+          err instanceof Error
+            ? err
+            : new Error("Failed to fetch completion detail")
+        );
+      } finally {
+        setIsLoading(false);
+      }
+    };
+
+    fetchCompletionDetail();
+  }, [id, client]);
+
+  return (
+    <ChatCompletionDetailView
+      completion={completionDetail}
+      isLoading={isLoading}
+      error={error}
+      id={id}
+    />
+  );
+}