fix(admin,api): honor STORAGE_IMPL when surfacing file_store backend (closes #17294) (#17441)

## Summary

When `STORAGE_IMPL=AWS_S3`, the Admin Service status page keeps showing
MinIO. Three things conspire:

1. `admin/server/config.py::load_configurations` only knows the
   `minio` and `minio_0` config keys. An `s3` block lands on the
   `case _:` branch and logs `Unknown configuration key: s3`
   (issue #17294).
2. `admin/server/services.py::ServiceMgr.get_all_services` filters
   retrieval services by `DOC_ENGINE` but has no equivalent filter
   for `file_store` services by `STORAGE_IMPL`. A stale MinIO block
   is returned regardless of the active backend.
3. The wired health check is hardcoded to `check_minio_alive`, which
   calls `settings.MINIO['host']`. With `STORAGE_IMPL=AWS_S3` that
   block is uninitialized, so the check always times out.


Fixes #17294

test/unit_test/api/utils/test_health_utils_s3.py

@@ -0,0 +1,84 @@
+#
+#  Copyright 2025 The InfiniFlow Authors. All Rights Reserved.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+"""
+Unit tests for the S3 file-store health check (check_s3_alive).
+Closes #17294 — Admin Service status used to silently show MinIO when
+STORAGE_IMPL=AWS_S3, because the only health check wired into the
+admin config loader was check_minio_alive.
+"""
+
+from unittest.mock import patch
+
+
+class TestCheckS3Alive:
+    """Test check_s3_alive delegates to the generic check_storage."""
+
+    @patch("api.utils.health_utils.check_storage")
+    def test_returns_alive_when_storage_healthy(self, mock_check_storage):
+        mock_check_storage.return_value = (True, {"elapsed": "12.3"})
+        from api.utils.health_utils import check_s3_alive
+
+        result = check_s3_alive()
+        assert result["status"] == "alive"
+        assert "elapsed" in result["message"]
+        mock_check_storage.assert_called_once_with()
+
+    @patch("api.utils.health_utils.check_storage")
+    def test_returns_timeout_when_storage_unhealthy(self, mock_check_storage):
+        mock_check_storage.return_value = (False, {"elapsed": "9.0", "error": "Connection refused"})
+        from api.utils.health_utils import check_s3_alive
+
+        result = check_s3_alive()
+        assert result["status"] == "timeout"
+        assert "Connection refused" in result["message"]
+
+    @patch("api.utils.health_utils.check_storage")
+    def test_returns_timeout_when_error_missing(self, mock_check_storage):
+        # Storage health returned False with no error key — must still
+        # surface a non-empty message so the admin UI doesn't render
+        # an empty status.
+        mock_check_storage.return_value = (False, {"elapsed": "1.0"})
+        from api.utils.health_utils import check_s3_alive
+
+        result = check_s3_alive()
+        assert result["status"] == "timeout"
+        assert "unknown" in result["message"]
+
+
+class TestCheckStorageDelegateContract:
+    """Verify check_s3_alive and check_storage stay in sync.
+
+    The S3 health check is a thin wrapper over check_storage so the
+    same code path works for AWS S3, MinIO, R2, etc. If check_storage's
+    return shape ever changes, these tests will fail and force a
+    companion update to check_s3_alive.
+    """
+
+    @patch("api.utils.health_utils.check_storage")
+    def test_message_includes_elapsed_from_storage(self, mock_check_storage):
+        mock_check_storage.return_value = (True, {"elapsed": "42.0"})
+        from api.utils.health_utils import check_s3_alive
+
+        result = check_s3_alive()
+        assert "42.0" in result["message"]
+
+    @patch("api.utils.health_utils.check_storage")
+    def test_message_includes_error_string(self, mock_check_storage):
+        mock_check_storage.return_value = (False, {"elapsed": "0.5", "error": "boom"})
+        from api.utils.health_utils import check_s3_alive
+
+        result = check_s3_alive()
+        assert "boom" in result["message"]