Fix lockfile show page not updating via Turbo

[JuanVqz]

Summary

• After Defer run_check! to Sidekiq to fix web dyno memory pressure #216 deferred run_check! to Sidekiq, the lockfile show page rendered before any LockfileCheck or GemCheck rows existed in the DB
• The page showed a blue "No checks have been run" alert; ResolveGem then broadcast updates to dom_id(gem_check) targets that were never in the DOM, so results only appeared after a manual refresh
• Fix: broadcast a full replace of the checks container from StartCheck right after create_for!, so all <tr id="gem_check_XYZ"> rows are rendered before individual resolve-gem broadcasts fire

Changes

• Extract _checks_container.html.erb and _lockfile_check_section.html.erb partials from inline show_new.html.erb
• Wrap checks area in <div id="lockfile_X_checks"> as a stable Turbo broadcast target
• StartCheck#perform reloads the association and broadcasts broadcast_replace_to after create_for! + enqueue_gem_checks
• Update "no checks" message to "Your lockfile is being processed..." so users know work is underway

Test plan

• Upload a Gemfile.lock with a Rails 7.x dependency via the UI
• Confirm the show page immediately renders the checks section with "Checking..." badge (no blue alert)
• Confirm individual gem rows update in place as ResolveGem jobs complete (no refresh needed)