fix(build): make rubocop invocation deterministic in make ready

Author: gildesmarais

Makefile

@@ -2,6 +2,8 @@
 
 .PHONY: help test lint lint-js lint-ruby lintfix lintfix-js lintfix-ruby setup dev clean frontend-setup check-frontend quick-check ready yard-verify-public-docs openapi openapi-verify openapi-client openapi-client-verify openapi-lint openapi-lint-redocly openapi-lint-spectral openai-lint-spectral test-frontend-e2e
 
+RUBOCOP_FLAGS ?= --cache false
+
 # Default target
 help: ## Show this help message
 	@echo "html2rss-web Development Commands"
@@ -60,7 +62,7 @@ lint: lint-ruby lint-js ## Run all linters (Ruby + Frontend) - errors when issue
 
 lint-ruby: ## Run Ruby linter (RuboCop) - errors when issues found
 	@echo "Running RuboCop linting..."
-	bundle exec rubocop
+	bundle exec rubocop $(RUBOCOP_FLAGS)
 	@echo "Running Zeitwerk eager-load check..."
 	bundle exec rake zeitwerk:verify
 	@echo "Running YARD public-method docs check..."