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/cmd/arrtrix/main.go

@@ -1,9 +1,8 @@
 package main
 
 import (
-	"maunium.net/go/mautrix/bridgev2/matrix/mxmain"
-
 	"sneeuwvlok/packages/arrtrix/pkg/connector"
+	"sneeuwvlok/packages/arrtrix/pkg/runtime"
 )
 
 var (
@@ -12,7 +11,7 @@ var (
 	BuildTime = "unknown"
 )
 
-var m = mxmain.BridgeMain{
+var m = runtime.Main{
 	Name:        "arrtrix",
 	URL:         "https://github.com/chris-kruining/sneeuwvlok",
 	Description: "An Arr-focused Matrix appservice bridge.",