Fix Docker command to remove Gemfile.lock before bundle install

Change command from "bundle update" to "rm -f Gemfile.lock && bundle install"
to avoid dependency conflicts between different Rails versions.

With "bundle update", the existing Gemfile.lock would cause version
resolution failures when switching between Rails versions, especially
when both activerecord and railties are specified with different
version requirements.

Removing Gemfile.lock ensures each container gets the correct
dependencies for its specified RAILS_VERSION environment variable.

Tested and verified all services pass:
- Rails 6.1.7.10: 674 runs, 8772 assertions, 0 failures ✅
- Rails 7.0.10: 674 runs, 8772 assertions, 0 failures ✅
- Rails 7.1.6: 674 runs, 8772 assertions, 0 failures ✅
- Rails 7.2.3: 674 runs, 8772 assertions, 0 failures ✅
- Rails 8.0.4: 674 runs, 8772 assertions, 0 failures ✅
- Rails 8.1.2: 674 runs, 8772 assertions, 0 failures ✅

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: takaokouji

docker-compose.yml

@@ -17,47 +17,47 @@ services:
     container_name: jsonapi-rails-6.1
     environment:
       - RAILS_VERSION=6.1.7.10
-    command: bash -c "bundle update && bundle exec rake test"
+    command: bash -c "rm -f Gemfile.lock && bundle install && bundle exec rake test"
 
   # Rails 7.0.10
   rails-7.0:
     <<: *test-base
     container_name: jsonapi-rails-7.0
     environment:
       - RAILS_VERSION=7.0.10
-    command: bash -c "bundle update && bundle exec rake test"
+    command: bash -c "rm -f Gemfile.lock && bundle install && bundle exec rake test"
 
   # Rails 7.1.6
   rails-7.1:
     <<: *test-base
     container_name: jsonapi-rails-7.1
     environment:
       - RAILS_VERSION=7.1.6
-    command: bash -c "bundle update && bundle exec rake test"
+    command: bash -c "rm -f Gemfile.lock && bundle install && bundle exec rake test"
 
   # Rails 7.2.3
   rails-7.2:
     <<: *test-base
     container_name: jsonapi-rails-7.2
     environment:
       - RAILS_VERSION=7.2.3
-    command: bash -c "bundle update && bundle exec rake test"
+    command: bash -c "rm -f Gemfile.lock && bundle install && bundle exec rake test"
 
   # Rails 8.0.4
   rails-8.0:
     <<: *test-base
     container_name: jsonapi-rails-8.0
     environment:
       - RAILS_VERSION=8.0.4
-    command: bash -c "bundle update && bundle exec rake test"
+    command: bash -c "rm -f Gemfile.lock && bundle install && bundle exec rake test"
 
   # Rails 8.1.2
   rails-8.1:
     <<: *test-base
     container_name: jsonapi-rails-8.1
     environment:
       - RAILS_VERSION=8.1.2
-    command: bash -c "bundle update && bundle exec rake test"
+    command: bash -c "rm -f Gemfile.lock && bundle install && bundle exec rake test"
 
   # Interactive shell for debugging (defaults to Rails 8.1)
   shell: