Port satlover.de dual-station pass matching feature:
- New feature/mutual module with mutual pass data model
- MutualViewModel: compute overlapping passes for two stations
- ElevationCurveChart: Canvas-based dual elevation curve with drag
- MutualScreen: input form + results with expandable cards
- Navigation: add Mutual tab to bottom navigation bar
- i18n: add Chinese/English strings for new feature
Complete rewrite inspired by Morse Expert / CW Skimmer (VE3NEA):
- CwFFT: radix-2 FFT (256-point) for time-frequency analysis
- CwSpectrogram: sliding-window waterfall (40 cols x 33 bins, 8ms resolution)
- CwBayesianDecoder: Gaussian probability replaces hard dit/dash thresholds
- CwChannelTracker: multi-channel peak detection (up to 3 signals)
- CwDecoder: integrates all components, monitors 200-1200 Hz simultaneously
Key advantages over v2 (ggmorse):
- Frequency-agnostic: full spectrum monitored, not locked to one tone
- Multi-channel: tracks multiple signals in parallel
- Bayesian: probability-based decisions, not hard ratios
- Doppler tolerant: frequency drift just moves energy between bins
- Add CwDsp with FIR bandpass filter, envelope detection, Goertzel tone detector
- Add CwDecoder with real-time Morse timing analysis and character lookup
- Add CW state/actions to RadarState, wire into RadarViewModel
- Add collapsible CW decoder panel to transceivers page
- 19 unit tests covering DSP, Morse table, and decoder state
- Shares IAudioCapture with SSTV, auto-stops SSTV when CW starts