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/tray/tray.go

@@ -14,7 +14,7 @@ import (
 	st "git.davoryn.de/calic/syncwarden/internal/syncthing"
 )
 
-const version = "0.2.0"
+const version = "0.3.0"
 
 // App manages the tray icon and Syncthing monitoring.
 type App struct {
@@ -54,12 +54,14 @@ func (a *App) onReady() {
 	if a.cfg.SyncthingAPIKey == "" {
 		if key, err := st.DiscoverAPIKey(); err == nil && key != "" {
 			a.cfg.SyncthingAPIKey = key
-			_ = config.Save(a.cfg)
+			if err := config.Save(a.cfg); err != nil {
+				log.Printf("config save error: %v", err)
+			}
 			log.Printf("auto-discovered Syncthing API key")
 		}
 	}
 
-	a.client = st.NewClient(a.cfg.BaseURL(), a.cfg.SyncthingAPIKey)
+	a.client = st.NewClient(a.cfg.BaseURL(), a.cfg.SyncthingAPIKey, a.cfg.SyncthingInsecureTLS)
 
 	// Check if Syncthing is installed
 	if !st.IsInstalled() {