## Summary
Parse and display per-hop SNR values from TRACE packets in the Packet
Byte Breakdown panel.
## Changes
### Backend (`cmd/server/decoder.go`)
- Added `SNRValues []float64` field to Payload struct
(`json:"snrValues,omitempty"`)
- In the TRACE-specific block, extract SNR from header path bytes before
they're overwritten with route hops
- Each header path byte is `int8(SNR_dB * 4.0)` per firmware — decode by
dividing by 4.0
### Frontend (`public/packets.js`)
- Added "SNR Path" section in `buildFieldTable()` showing per-hop SNR
values in dB when packet type is TRACE
- Added TRACE-specific payload rendering (trace tag, auth code, flags
with hash_size, route hops)
## TDD
- Red commit: `4dba4e8` — test asserts `Payload.SNRValues` field
(compile fails, field doesn't exist)
- Green commit: `5a496bd` — implementation passes all tests
## Testing
- `go test ./...` passes (all existing + 2 new TRACE SNR tests)
- No frontend test changes needed (no existing TRACE UI tests; rendering
is additive)
Fixes#979
---------
Co-authored-by: you <you@example.com>
