Add optional payload decoding to the packet capture service. GRP_TXT
channel messages are decrypted (sender/text), ADVERTs are parsed
(name/role/lat-lon), and a nested "decoded" object is attached to each
packet alongside the unchanged raw fields.
- Comprehensive channel key store: bot's configured radio channels plus
decode_hashtag_channels, [Channels_List], decode_channel_keys, and the
built-in default Public key.
- Publishing the decoded object to MQTT is off by default and
configurable per broker via mqttN_include_decoded.
- Configurable packet-log rotation (off/size/time) for historical dumps.
The decoder lives in a standalone, dependency-free module
(modules/meshcore_payload_decode.py) so it can be shared verbatim with
the meshcore-packet-capture project.
Closes#197Closes#35