feat(config): add security feature toggle support

Implements a master toggle for security features across config,
CLI, and application logic. This allows granular control over
whether the advanced security middleware and protections are
active globally.

lib/config/models.go

@@ -37,6 +37,7 @@ const (
 	SettingThumbnailIntervalSeconds  = "thumbnail_interval_seconds"
 	SettingDataDir                   = "data_dir"
 	SettingActivityRetentionSeconds  = "activity_retention_seconds"
+	SettingSecurityEnabled           = "security_enabled"
 	SettingSecurityIPWhitelist       = "security_ip_whitelist"
 	SettingSecurityAdminIPWhitelist  = "security_admin_ip_whitelist"
 	SettingTrustedProxyCIDRs         = "trusted_proxy_cidrs"
@@ -108,6 +109,7 @@ type Config struct {
 	ThumbnailBatchSize          int
 	ThumbnailIntervalSeconds    int
 	ActivityRetentionSeconds    int64
+	SecurityEnabled             bool
 	SecurityIPWhitelist         string
 	SecurityAdminIPWhitelist    string
 	TrustedProxyCIDRs           string