When the PacketProducer buffer crosses 80% capacity, signal Aprsme.Is
to switch its TCP socket to passive mode, leveraging TCP flow control
to slow APRS-IS intake. Resume active mode when buffer drains below 30%.
A 30-second safety valve timer auto-resumes if backpressure gets stuck.
Disconnect/reconnect/terminate paths all clear backpressure state.
- Switch PacketProducer buffer from list to :queue for O(1) overflow handling
- Add cached leadership check via :persistent_term to eliminate GenServer.call
bottleneck in packet distribution hot path
- Simplify packets_live coordinate extraction from 70 lines of nested
conditionals to helper functions (extract_coordinate/2, format_coordinate/1)
- Remove debug logging from hot paths (packets.ex queries, PacketDistributor,
app.js console.logs)
- Remove sobelow dependency (false positives blocking commits)
- Add 25 new tests for PacketProducer, coordinate helpers, and cached leadership
