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>

.golangci.yml

@@ -0,0 +1,13 @@
+linters:
+  enable:
+    - errcheck
+    - gosec
+    - govet
+    - ineffassign
+    - staticcheck
+    - unused
+
+issues:
+  exclude-dirs:
+    - cmd/panel
+    - cmd/icongen