- Remove unused @is_public_view variable from controller
- Simplify conditionals by leveraging methods that return [] when empty
- Move public view from trips/public_show to shared/trips/show (Rails conventions)
- Refactor trips#update to be HTML-only (remove JSON responses)
- Convert sharing form to use proper Rails form helpers
- Move JS controller to shared/ subdirectory with proper namespacing
- Create RSpec shared examples for Shareable concern to eliminate duplication
- Update request specs to match HTML-only controller behavior
- Apply 'render/redirect ... and return' pattern for early returns
