v0.3.0: fix HTTP client leak, add tests and CI pipeline

Reuse a single long-poll HTTP client instead of creating one per
Events() call (~every 30s). Make TLS skip-verify configurable via
syncthing_insecure_tls. Log previously swallowed config errors.
Add unit tests for all monitor trackers, config, and state logic.
Add CI workflow (vet, golangci-lint, govulncheck, go test -race).

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

internal/monitor/monitor.go

@@ -82,7 +82,9 @@ func (m *Monitor) Stop() {
 	m.mu.Lock()
 	m.cfg.LastEventID = m.events.LastEventID()
 	m.mu.Unlock()
-	_ = config.Save(m.cfg)
+	if err := config.Save(m.cfg); err != nil {
+		log.Printf("config save error: %v", err)
+	}
 }
 
 func (m *Monitor) pollLoop() {