addFromContact: Don't auto-favorite when CLIENT_BASE; don't update last_heard unless CLIENT_BASE

[compumike]

Clients are now sending an add_contact AdminMessage before basically every text message DM (because clients may hold a larger node database with public keys than the radio holds).

This has two unintended side effects:

1. The destination node's last_heard is getting incorrectly updated to the current time even when we just send them a DM.
2. For CLIENT_BASE, the auto-favoriting in NodeDB::addFromContact may be causing unintentional routing issues. (Discussion) For CLIENT_BASE we should only do explicit favoriting.

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This PR makes the following changes:

• NodeDB::addFromContact
  • don't auto-favorite if we're CLIENT_BASE
  • don't update last_heard (unless we're CLIENT_BASE -- see comment in code below)
  • if should_ignore then also clear the is_favorite flag
• AdminModule::handleReceivedProtobuf
  • don't auto-favorite if we're CLIENT_BASE

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Client Possible Issues

I have tested this, and think this should be generally safe, but there are two tiny issues that clients may want to take a look at:

1. Will any clients break if they see a NodeInfo with last_heard == 0? This could happen now if they do an add_contact for a node that's been evicted.
2. Clients may assume that whenever they send add_contact that the node will become favorited, and may update their local database accordingly. (This appears to be true in the iOS client, at least -- taking a look now.)

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Future follow-ups

• a few small PRs in clients:
  • make sure clients don't do their own auto-favoriting while in CLIENT_BASE
  • make it so favoriting while in CLIENT_BASE is more explicit, possibly a Yes/No confirm dialog.
  • make it so that when switching from any other role to CLIENT_BASE, we give some sort of message about removing any favorited nodes that are not in their control

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🤝 Attestations

• I have tested that my proposed changes behave as described.
• I have tested that my proposed changes do not cause any obvious regressions on the following devices:
  • Heltec (Lora32) V3

[GUVWAF]

Looks good to me from a firmware point-of-view, but indeed might need some additional checks in the clients.

[compumike]

Looks good to me from a firmware point-of-view, but indeed might need some additional checks in the clients.

@GUVWAF Excellent, thanks. I just created a feature request issue here: "[Feature Request]: CLIENT_BASE: make it harder to 'accidentally' favorite other nodes" #8514 to track the broader topic, including revisions to client apps!