refactor: extract pagination logic into shared helper function

Move pagination logic from LocalFS and HuggingFace implementations into
a common helper function to ensure consistent pagination behavior across
providers. This reduces code duplication and centralizes pagination
logic in one place.

Signed-off-by: Sébastien Han <seb@redhat.com>

llama_stack/apis/common/responses.py

@@ -0,0 +1,23 @@
+# 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.
+
+from typing import Any, Dict, List
+
+from pydantic import BaseModel
+
+from llama_stack.schema_utils import json_schema_type
+
+
+@json_schema_type
+class PaginatedResponse(BaseModel):
+    """A generic paginated response that follows a simple format.
+
+    :param data: The list of items for the current page
+    :param has_more: Whether there are more items available after this set
+    """
+
+    data: List[Dict[str, Any]]
+    has_more: bool