Implement Substation: BLE-WS bridge with music-reactive e-stim

- Renamed from CoyoteBridge to Substation (namespace, classes, UI)
- BLE connection via WinRT with graceful disconnect handling
- WebSocket server (127.0.0.1:8765) with single-client, push events
  for BLE connect/disconnect transitions
- Operator strength limiter (clamp/scale modes, default 30)
- Tray icon with 3 states: neutral/active/hot (runtime-drawn voltage glyph)
- A/B strength gauges, hide-on-minimise to tray
- Music mode: MP3 decode + FFT analysis (NAudio + FftSharp), rhythm→ch A,
  melody→ch B, pre-analyzed with synced audio playback
- Test/Stop All work without BLE connected (dev mode)
- WS device-driving commands error when BLE not connected; ping/status/
  connect always work
- TreatWarningsAsErrors, LangVersion=latest
- .gitignore, README with full API docs + attribution

.gitignore

@@ -0,0 +1,33 @@
+## .NET build output
+bin/
+obj/
+
+## User-specific files
+*.user
+*.suo
+*.userprefs
+*.vs/
+*.DotSettings.user
+
+## NuGet
+*.nupkg
+*.snupkg
+**/[Pp]ackages/*
+!*.build.props
+!*.build.targets
+
+## Visual Studio / Rider / VS Code
+.idea/
+.vscode/
+*.sln.docstates
+
+## OS files
+Thumbs.db
+ehthumbs.db
+Desktop.ini
+.DS_Store
+
+## Logs / temp
+*.log
+tmp/
+*.tmp