Control allowance of root multi-lvl wildcard subscription creation

[dmytro-landiak]

Pull Request description

Controls whether clients are permitted to subscribe to the root multi-level wildcard "#".

• If set to true (default):
  Clients can subscribe to "#", receiving a copy of EVERY message published to the broker.
  This is useful for debugging or firehose-style monitoring services.
• If set to false:
  Clients are explicitly denied permission to subscribe to the exact topic "#".
  They can still subscribe to specific paths (e.g., "sensors/#") or individual topics.
  Recommended for production to prevent accidental or malicious data leakage

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Back-End feature checklist

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