[feat](trx-wefax): implement WEFAX decoder with full server and frontend integration

Pure Rust WEFAX (Weather Facsimile) decoder supporting 60/90/120/240 LPM,
IOC 288 and 576, with automatic APT tone detection and phase alignment.

Core DSP pipeline:
- Polyphase rational resampler (48k→11025 Hz)
- FM discriminator (Hilbert FIR + instantaneous frequency)
- Goertzel tone detector (300/450/675 Hz APT tones)
- Phase alignment via cross-correlation on phasing signal
- Line slicer with linear interpolation pixel clock recovery
- Image assembler with PNG encoding

State machine: Idle→StartDetected→Phasing→Receiving→Stopping

Server integration:
- WefaxMessage/WefaxProgress in trx-core DecodedMessage
- DecoderConfig, DecoderResetSeqs, RigCommand wefax variants
- DECODER_REGISTRY entry in trx-protocol
- DecoderHistories/DecoderLoggers wefax support
- run_wefax_decoder() async task in trx-server audio.rs
- History persistence in pickledb store

Frontend integration:
- wefax.js plugin with live canvas rendering and gallery
- HTML sub-tab with canvas, gallery, toggle/clear controls
- SSE dispatch for wefax/wefax_progress events
- Decode history worker and restore support
- Toggle/clear API endpoints

19 unit tests covering resampler, FM discriminator, tone detection,
phasing, line slicing, image encoding, and decoder state machine.

https://claude.ai/code/session_019eyxgx3LuhcFZ7T5tr2Trm
Signed-off-by: Claude <noreply@anthropic.com>

Cargo.toml

@@ -12,6 +12,7 @@ members = [
     "src/decoders/trx-ftx",
     "src/decoders/trx-rds",
     "src/decoders/trx-vdes",
+    "src/decoders/trx-wefax",
     "src/decoders/trx-wspr",
     "src/trx-core",
     "src/trx-protocol",