feat(config): add expired box cleanup functionality

Adds dedicated config setting and cleanup logic for
managing expired content boxes via admin tools and CLI.

lib/config/overrides.go

@@ -131,6 +131,8 @@ func (cfg *Config) assignInt64(key string, value int64, source Source) {
 		cfg.SecurityUploadWindowSeconds = value
 	case SettingSecurityUploadMaxGB:
 		cfg.SecurityUploadMaxBytes = value
+	case SettingExpiredCleanupIntervalSecs:
+		cfg.ExpiredCleanupIntervalSeconds = value
 	}
 	if key == SettingGlobalMaxFileSizeBytes || key == SettingGlobalMaxBoxSizeBytes || key == SettingDefaultUserMaxFileBytes || key == SettingDefaultUserMaxBoxBytes || key == SettingSecurityUploadMaxGB {
 		cfg.setValue(key, formatGigabytesFromBytes(value), source)