Update Ruby version to 3.1 in GitHub Actions workflows

Bundler 2.6.3 requires Ruby >= 3.1.0, but workflows were using Ruby 3.0.7,
causing build failures. Updated both release and bump-build workflows to use
Ruby 3.1.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.github/workflows/bump-build.yml

@@ -17,7 +17,7 @@ jobs:
           git config --local user.name "github-actions[bot]"
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: '3.0'
+          ruby-version: '3.1'
           bundler-cache: true
       - uses: maierj/fastlane-action@v3.0.0
         with:

.github/workflows/release.yml

@@ -32,7 +32,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: '3.0'
+          ruby-version: '3.1'
           bundler-cache: true
           cache-version: 1
       - name: Replace signing certificate to AppStore
@@ -57,7 +57,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: '3.0'
+          ruby-version: '3.1'
           bundler-cache: true
           cache-version: 1
       - name: Replace signing certificate to Direct with Developer ID