Update Ruby version in Dockerfile and configuration to 3.4

Author: andy1li

dockerfiles/ruby-3.4.Dockerfile

@@ -0,0 +1,19 @@
+# syntax=docker/dockerfile:1.7-labs
+FROM ruby:3.4-alpine3.23
+
+# Required for installing the json/async gems
+RUN apk add --no-cache \
+    build-base~=0.5 \
+    libssl3~=3.5 \
+    readline-dev~=8.3 \
+    zlib-dev~=1.3
+
+# Re-build if Gemfile or Gemfile.lock changes
+ENV CODECRAFTERS_DEPENDENCY_FILE_PATHS="Gemfile,Gemfile.lock"
+
+WORKDIR /app
+
+# .git & README.md are unique per-repository. We ignore them on first copy to prevent cache misses
+COPY --exclude=.git --exclude=README.md . /app
+
+RUN bundle install --verbose

starter_templates/ruby/config.yml

@@ -1,3 +1,3 @@
 attributes:
-  required_executable: ruby (2.7)
+  required_executable: ruby (3.4)
   user_editable_file: app/server.rb