Feature/ping uid privacy

[fauxreigner-mb]

Problem

Pings broadcast @[MapperBot] LAT, LON in a public channel. Power has already been moved to the API payload, but coordinates remained. This is privacy risk since anyone on the channel could read the sender's location in plaintext. Anonymous mode is meant to combat this but still broadcasts the information and must be enabled.

Change

Replace the message text with a 6-char hex UID derived from a hash of the coordinates + timestamp, masked to 3 bytes. Coordinates stay in the API payload only. sendPing in connection.dart is simplified to accept the pre-built message string rather than lat/lon.

Why This Fixes It

TxTracker can still confirm an echo is ours via message content matching, but the message itself reveals nothing about the sender's location. ~16.7M options should be sufficiently unique in the listening window and keeps the message short.

[MrAlders0n]

@fauxreigner-mb I do like this, give me a bit to review, I've been underwater. Appreciate you working on this!

[MrAlders0n]

@CSP-Tom This proposal removes coordinates from the channel message altogether and instead uses a unique hash.

Lets chat about this :)

[fauxreigner-mb]

@MrAlders0n no worries, appreciate you taking the time to review. There are definitely "better" ways to generate the message hash, either in the crypto.dart package or roll your own using dart:math, but using the .hashCode property seems good enough and keeps it simple.

[446564]

changed to draft until a consensus is reached