Manage sequence numbers on Peer control accounts

[mikera]

Currently, there is a risk of sequence number mismatch between:

• Peers submitting their own transactions (e.g. adjusting URL)
• Clients controlling the Peer Controller Account remotely (having the right keypair)

Ideally, both of these should be able to synchronise, but this is problematic as two clients aren't supposed to simultaneously issue transactions for the same account independently.

Possible solutions:

• Peer operators choose one, but not both, of the above models
• Specialised Convex instance for managing Peers
• Servers tracking sequence numbers for their Peer instance