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/server/validation.go

@@ -156,6 +156,9 @@ func (app *App) maxRequestBodyBytes() int64 {
 }
 
 func (app *App) enforceUploadRateLimit(ctx *gin.Context, size int64) bool {
+	if !app.securityFeaturesEnabled() || app.securityGuard == nil {
+		return true
+	}
 	ip := app.clientIP(ctx)
 	if app.securityGuard.IsWhitelisted(ip) || app.securityGuard.IsAdminWhitelisted(ip) {
 		return true