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/connector.go

@@ -3,6 +3,7 @@ package connector
 import (
 	"context"
 	"fmt"
+	"net/http"
 
 	"maunium.net/go/mautrix/bridgev2"
 	"maunium.net/go/mautrix/bridgev2/database"
@@ -17,6 +18,7 @@ type ArrtrixConnector struct {
 }
 
 var _ bridgev2.NetworkConnector = (*ArrtrixConnector)(nil)
+var _ interface{ MountRoutes(*http.ServeMux) error } = (*ArrtrixConnector)(nil)
 
 func (s *ArrtrixConnector) GetName() bridgev2.BridgeName {
 	return bridgev2.BridgeName{