Fix code review findings batch 2: dead code, encoding, correctness
- Delete dead modules: Archiver, PacketPipelineSetup, SystemMonitor
- Encoding: fast-path for clean ASCII, fix latin1 C1 control chars (128-159)
- SpatialPubSub: fix date line grid cell wrapping
- QueryBuilder: use indexed has_weather column instead of 10-way OR
- PacketProcessor/HistoricalLoader: wire up heat map via DisplayManager
- MapLive: add PacketBatcher crash recovery with Process.monitor
- MapLive: fix time display re-render by touching assign
- DeviceCache: remove unreachable outer try/rescue
- Remove dead stubs: RateLimiterWrapper count/reset, DeviceIdentification enqueue_refresh_job
- Simplify Application.pubsub_config/0
- Add tests for SpatialPubSub, PacketBatcher, encoding, weather_only