Add a `MaxMessageSize` entry to `NodeInfoId` so the max message size
(in bytes) accepted by the relay protocol can be queried through the
node info surface, consumed by both the debug API and the FFI
`get_node_info` / `get_available_node_info_ids` calls.
The value is read from the mounted relay's `maxMessageSize` and is empty
when the relay protocol is not mounted on the node (e.g. light nodes),
mirroring the existing `MyMixPubKey` handling.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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