Implement SyncWarden v0.1.0

Full Syncthing tray wrapper with:
- System tray with 5 icon states (idle/syncing/paused/error/disconnected)
- Syncthing REST API client with auto-discovered API key
- Long-polling event listener for real-time status
- Transfer rate monitoring, folder tracking, recent files, conflict counting
- Full context menu with folders, recent files, settings toggles
- Embedded admin panel binary (webview, requires CGO)
- OS notifications via beeep (per-event configurable)
- Syncthing process management with auto-restart
- Cross-platform installer with autostart
- CI pipeline for Linux (.deb + .tar.gz) and Windows (.zip)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/monitor/speed.go

@@ -0,0 +1,52 @@
+package monitor
+
+import (
+	"sync"
+	"time"
+)
+
+// SpeedTracker calculates transfer rates by diffing byte counters.
+type SpeedTracker struct {
+	mu       sync.Mutex
+	lastIn   int64
+	lastOut  int64
+	lastTime time.Time
+	downRate float64
+	upRate   float64
+}
+
+// NewSpeedTracker creates a new speed tracker.
+func NewSpeedTracker() *SpeedTracker {
+	return &SpeedTracker{}
+}
+
+// Update records new byte counters and calculates rates.
+func (s *SpeedTracker) Update(inBytes, outBytes int64) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	now := time.Now()
+	if !s.lastTime.IsZero() {
+		dt := now.Sub(s.lastTime).Seconds()
+		if dt > 0 {
+			s.downRate = float64(inBytes-s.lastIn) / dt
+			s.upRate = float64(outBytes-s.lastOut) / dt
+			if s.downRate < 0 {
+				s.downRate = 0
+			}
+			if s.upRate < 0 {
+				s.upRate = 0
+			}
+		}
+	}
+	s.lastIn = inBytes
+	s.lastOut = outBytes
+	s.lastTime = now
+}
+
+// Rates returns the current download and upload rates in bytes/sec.
+func (s *SpeedTracker) Rates() (down, up float64) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.downRate, s.upRate
+}