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/onboarding/welcome_test.go

@@ -0,0 +1,56 @@
+package onboarding
+
+import (
+	"strings"
+	"testing"
+
+	"maunium.net/go/mautrix/bridgev2/bridgeconfig"
+	"maunium.net/go/mautrix/id"
+)
+
+func TestComposeWelcomeMessageDefaults(t *testing.T) {
+	out := composeWelcomeMessage(
+		"Arrtrix",
+		"!arr",
+		id.UserID("@arrtrixbot:test"),
+		bridgeconfig.ManagementRoomTexts{},
+		false,
+		true,
+	)
+
+	for _, fragment := range []string{
+		"Hello, I'm the Arrtrix bot.",
+		"This room has been marked as your management room.",
+		"Use `help` to see the commands available right now.",
+	} {
+		if !strings.Contains(out, fragment) {
+			t.Fatalf("expected welcome output to contain %q, got:\n%s", fragment, out)
+		}
+	}
+}
+
+func TestComposeWelcomeMessageTemplateValues(t *testing.T) {
+	out := composeWelcomeMessage(
+		"Arrtrix",
+		"!arr",
+		id.UserID("@arrtrixbot:test"),
+		bridgeconfig.ManagementRoomTexts{
+			Welcome:          "Welcome to $bridge.",
+			WelcomeConnected: "Talk to $bot with $cmdprefix help.",
+			AdditionalHelp:   "Custom footer for $bridge.",
+		},
+		true,
+		false,
+	)
+
+	for _, fragment := range []string{
+		"Welcome to Arrtrix.",
+		"Use `!arr help` to see available commands in this room.",
+		"Talk to @arrtrixbot:test with !arr help.",
+		"Custom footer for Arrtrix.",
+	} {
+		if !strings.Contains(out, fragment) {
+			t.Fatalf("expected templated welcome output to contain %q, got:\n%s", fragment, out)
+		}
+	}
+}