chore(rename): move llama_stack.distribution to llama_stack.core (#2975)

We would like to rename the term `template` to `distribution`. To
prepare for that, this is a precursor.

cc @leseb

llama_stack/core/ui/app.py

@@ -0,0 +1,55 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+import streamlit as st
+
+
+def main():
+    # Evaluation pages
+    application_evaluation_page = st.Page(
+        "page/evaluations/app_eval.py",
+        title="Evaluations (Scoring)",
+        icon="📊",
+        default=False,
+    )
+    native_evaluation_page = st.Page(
+        "page/evaluations/native_eval.py",
+        title="Evaluations (Generation + Scoring)",
+        icon="📊",
+        default=False,
+    )
+
+    # Playground pages
+    chat_page = st.Page("page/playground/chat.py", title="Chat", icon="💬", default=True)
+    rag_page = st.Page("page/playground/rag.py", title="RAG", icon="💬", default=False)
+    tool_page = st.Page("page/playground/tools.py", title="Tools", icon="🛠", default=False)
+
+    # Distribution pages
+    resources_page = st.Page("page/distribution/resources.py", title="Resources", icon="🔍", default=False)
+    provider_page = st.Page(
+        "page/distribution/providers.py",
+        title="API Providers",
+        icon="🔍",
+        default=False,
+    )
+
+    pg = st.navigation(
+        {
+            "Playground": [
+                chat_page,
+                rag_page,
+                tool_page,
+                application_evaluation_page,
+                native_evaluation_page,
+            ],
+            "Inspect": [provider_page, resources_page],
+        },
+        expanded=False,
+    )
+    pg.run()
+
+
+if __name__ == "__main__":
+    main()