Add Arrtrix runtime, config, onboarding, and webhook support

- Implement runtime package for bridge startup, config loading, and env
  overrides
- Add onboarding package for management room welcome messages
- Add matrixcmd package for command processing and help
- Add webhook package with Radarr webhook support and validation
- Extend connector config for webhooks and validation
- Update default config and example config for new options
- Add tests for new packages and config validation
- Change database type default to sqlite3-fk-wal

packages/arrtrix/pkg/connector/config_test.go

@@ -0,0 +1,23 @@
+package connector
+
+import "testing"
+
+func TestConfigDefaultsApplyRadarrWebhookPath(t *testing.T) {
+	var cfg Config
+
+	cfg.applyDefaults()
+
+	if cfg.Webhooks.Radarr.Path == "" {
+		t.Fatal("expected radarr webhook path default to be set")
+	}
+}
+
+func TestConfigValidateRejectsEnabledWebhookWithoutSecret(t *testing.T) {
+	cfg := Config{}
+	cfg.Webhooks.Radarr.Enabled = true
+	cfg.applyDefaults()
+
+	if err := cfg.Validate(); err == nil {
+		t.Fatal("expected missing secret to fail validation")
+	}
+}