fix(helm): make the loki-sc-rules sidecar container compatible with the most recent versions of k8s-sidecar

[dcoppa]

What this PR does / why we need it:

When trying to use a k8s-sidecar version ≥ 2.x, the loki-sc-rules container crashes with the following error message:

{"time": "2025-12-08T14:07:21.551765+00:00", "level": "INFO", "msg": "Starting collector"}
{"time": "2025-12-08T14:07:21.644201+00:00", "level": "INFO", "msg": "No folder annotation was provided, defaulting to k8s-sidecar-target-directory"}
{"time": "2025-12-08T14:07:21.644497+00:00", "level": "INFO", "msg": "Loading incluster config..."}
{"time": "2025-12-08T14:07:21.645369+00:00", "level": "INFO", "msg": "Unique filenames will not be enforced."}
{"time": "2025-12-08T14:07:21.647169+00:00", "level": "INFO", "msg": "5xx response content will not be enabled."}
{"time": "2025-12-08T14:07:21.647701+00:00", "level": "INFO", "msg": "Performing initial list-based sync before starting watch."}
{"time": "2025-12-08T14:07:21.647922+00:00", "level": "INFO", "msg": "Loading incluster config..."}
{"time": "2025-12-08T14:07:21.649807+00:00", "level": "INFO", "msg": "Performing list-based sync on secret resources: {'namespace': 'loki'}"}
{"time": "2025-12-08T14:07:21.861818+00:00", "level": "INFO", "msg": "Loading incluster config..."}
{"time": "2025-12-08T14:07:21.862525+00:00", "level": "INFO", "msg": "Performing list-based sync on configmap resources: {'namespace': 'loki'}"}
{"time": "2025-12-08T14:07:22.150797+00:00", "level": "INFO", "msg": "Started server process [1]", "color_message": "Started server process [\u001b[36m%d\u001b[0m]"}
{"time": "2025-12-08T14:07:22.151111+00:00", "level": "INFO", "msg": "Waiting for application startup."}
{"time": "2025-12-08T14:07:22.243831+00:00", "level": "INFO", "msg": "Application startup complete."}
{"time": "2025-12-08T14:07:22.243506+00:00", "level": "INFO", "msg": "Writing /rules/fake/grafana.yaml (ascii)"}
{"time": "2025-12-08T14:07:22.245523+00:00", "level": "INFO", "msg": "Uvicorn running on http://0.0.0.0:8080 (Press CTRL+C to quit)", "color_message": "Uvicorn running on \u001b[1m%s://%s:%d\u001b[0m (Press CTRL+C to quit)"}
{"time": "2025-12-08T14:07:22.246109+00:00", "level": "INFO", "msg": "Initial sync complete, sidecar is ready."}
{"time": "2025-12-08T14:07:22.347746+00:00", "level": "ERROR", "msg": "FileNotFoundError: [Errno 2] No usable temporary directory found in ['/tmp', '/var/tmp', '/usr/tmp', '/app']", "exc_info": "Traceback (most recent call last):\n  File \"/app/sidecar.py\", line 158, in <module>\n    main()\n    ~~~~^^\n  File \"/app/sidecar.py\", line 152, in main\n    watch_for_changes(method, label, label_value, target_folder, request_url, request_method, request_payload,\n    ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n                      namespace, folder_annotation, resources, unique_filenames, script, enable_5xx,\n                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n                      ignore_already_processed, resource_name)\n                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/app/resources.py\", line 442, in watch_for_changes\n    processes = _start_watcher_processes(current_namespace, folder_annotation, label,\n                                         label_value, request_method, mode, request_payload, resources,\n                                         target_folder, unique_filenames, script, request_url, enable_5xx,\n                                         ignore_already_processed, resource_name)\n  File \"/app/resources.py\", line 481, in _start_watcher_processes\n    proc.start()\n    ~~~~~~~~~~^^\n  File \"/usr/local/lib/python3.14/multiprocessing/process.py\", line 121, in start\n    self._popen = self._Popen(self)\n                  ~~~~~~~~~~~^^^^^^\n  File \"/usr/local/lib/python3.14/multiprocessing/context.py\", line 224, in _Popen\n    return _default_context.get_context().Process._Popen(process_obj)\n           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^\n  File \"/usr/local/lib/python3.14/multiprocessing/context.py\", line 300, in _Popen\n    return Popen(process_obj)\n  File \"/usr/local/lib/python3.14/multiprocessing/popen_forkserver.py\", line 35, in __init__\n    super().__init__(process_obj)\n    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^\n  File \"/usr/local/lib/python3.14/multiprocessing/popen_fork.py\", line 20, in __init__\n    self._launch(process_obj)\n    ~~~~~~~~~~~~^^^^^^^^^^^^^\n  File \"/usr/local/lib/python3.14/multiprocessing/popen_forkserver.py\", line 51, in _launch\n    self.sentinel, w = forkserver.connect_to_new_process(self._fds)\n                       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^\n  File \"/usr/local/lib/python3.14/multiprocessing/forkserver.py\", line 89, in connect_to_new_process\n    self.ensure_running()\n    ~~~~~~~~~~~~~~~~~~~^^\n  File \"/usr/local/lib/python3.14/multiprocessing/forkserver.py\", line 156, in ensure_running\n    address = connection.arbitrary_address('AF_UNIX')\n  File \"/usr/local/lib/python3.14/multiprocessing/connection.py\", line 79, in arbitrary_address\n    return tempfile.mktemp(prefix='sock-', dir=util.get_temp_dir())\n                                               ~~~~~~~~~~~~~~~~~^^\n  File \"/usr/local/lib/python3.14/multiprocessing/util.py\", line 212, in get_temp_dir\n    base_tempdir = _get_base_temp_dir(tempfile)\n  File \"/usr/local/lib/python3.14/multiprocessing/util.py\", line 169, in _get_base_temp_dir\n    base_tempdir = tempfile.gettempdir()\n  File \"/usr/local/lib/python3.14/tempfile.py\", line 316, in gettempdir\n    return _os.fsdecode(_gettempdir())\n                        ~~~~~~~~~~~^^\n  File \"/usr/local/lib/python3.14/tempfile.py\", line 309, in _gettempdir\n    tempdir = _get_default_tempdir()\n  File \"/usr/local/lib/python3.14/tempfile.py\", line 224, in _get_default_tempdir\n    raise FileNotFoundError(_errno.ENOENT,\n                            \"No usable temporary directory found in %s\" %\n                            dirlist)\nFileNotFoundError: [Errno 2] No usable temporary directory found in ['/tmp', '/var/tmp', '/usr/tmp', '/app']"}

My PR fixes the helm chart: the same "tmp" emptyDir volume used in the main loki container is also mounted in the loki-sc-rules container.

Special notes for your reviewer:

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• [] Documentation added
• [] Tests updated
• Title matches the required conventional commits format, see here
  • Note that Promtail is considered to be feature complete, and future development for logs collection will be in Grafana Alloy. As such, feat PRs are unlikely to be accepted unless a case can be made for the feature actually being a bug fix to existing behavior.
• [] Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• [] If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR

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