[Feature] Add Calendar minimum date support

[djalmaaraujo]

Summary

• Add a Calendar min_date API and emit the value to the Stimulus controller
• Render dates before min_date with a disabled template and ignore disabled-day selection in JS
• Normalize date parsing to avoid YYYY-MM-DD timezone drift
• Add docs examples and component coverage

Closes #351

Testing

• docker run --rm -v ruby_ui_bundle:/usr/local/bundle -v /Users/djalmaaraujo/dev/linkana/ruby_ui-issue-351:/workspace -w /workspace/gem ruby:3.4.7 bash -lc 'bundle install && bundle exec rake test TEST=test/ruby_ui/calendar_test.rb'
• docker run --rm -v ruby_ui_bundle:/usr/local/bundle -v /Users/djalmaaraujo/dev/linkana/ruby_ui-issue-351:/workspace -w /workspace/gem ruby:3.4.7 bash -lc 'bundle install && bundle exec standardrb lib/ruby_ui/calendar/calendar.rb lib/ruby_ui/calendar/calendar_days.rb lib/ruby_ui/calendar/calendar_docs.rb test/ruby_ui/calendar_test.rb'
• node --check gem/lib/ruby_ui/calendar/calendar_controller.js
• node --check docs/app/javascript/controllers/ruby_ui/calendar_controller.js