Upgrade runtime to Ruby 4.0.9 (#381)

* Upgrade runtime to Ruby 4.0.9

Ruby 4.0.9 fixes the Regexp compilation bug behind GitLab's
CVE-2026-110264. Move `.ruby-version`, `Dockerfile` and
`Dockerfile-export` to it.

ref: https://www.ruby-lang.org/en/news/2026/10/23/ruby-4-0-9-released/

* Bump setup-ruby to v1.334.0 for Ruby 4.0.9

The pinned v1.327.0 and v1.324.0 did not know Ruby 4.0.9, so every CI
job failed at Ruby setup. v1.334.0 is the first release that does.

.github/workflows/ci.yml

@@ -21,7 +21,7 @@ jobs:
           persist-credentials: false
 
       - name: Set up Ruby
-        uses: ruby/setup-ruby@14594264cd68ce8a2345dd349bc3d138a4ef85c8 # v1.327.0
+        uses: ruby/setup-ruby@26e5b7d197ebf60545ee9667bcbace0be11ccaec # v1.334.0
         with:
           ruby-version: .ruby-version
           bundler-cache: true
@@ -40,7 +40,7 @@ jobs:
           persist-credentials: false
 
       - name: Set up Ruby
-        uses: ruby/setup-ruby@14594264cd68ce8a2345dd349bc3d138a4ef85c8 # v1.327.0
+        uses: ruby/setup-ruby@26e5b7d197ebf60545ee9667bcbace0be11ccaec # v1.334.0
         with:
           ruby-version: .ruby-version
           bundler-cache: true
@@ -63,7 +63,7 @@ jobs:
           persist-credentials: false
 
       - name: Set up Ruby
-        uses: ruby/setup-ruby@a0102e0972be65f351c307e2d64b9314a57c8073 # v1.324.0
+        uses: ruby/setup-ruby@26e5b7d197ebf60545ee9667bcbace0be11ccaec # v1.334.0
         with:
           ruby-version: .ruby-version
           bundler-cache: true
@@ -110,7 +110,7 @@ jobs:
           persist-credentials: false
 
       - name: Set up Ruby
-        uses: ruby/setup-ruby@14594264cd68ce8a2345dd349bc3d138a4ef85c8 # v1.327.0
+        uses: ruby/setup-ruby@26e5b7d197ebf60545ee9667bcbace0be11ccaec # v1.334.0
         env:
           REDIS_URL: redis://localhost:6379/0
         with:
@@ -143,7 +143,7 @@ jobs:
           persist-credentials: false
 
       - name: Set up Ruby
-        uses: ruby/setup-ruby@14594264cd68ce8a2345dd349bc3d138a4ef85c8 # v1.327.0
+        uses: ruby/setup-ruby@26e5b7d197ebf60545ee9667bcbace0be11ccaec # v1.334.0
         env:
           REDIS_URL: redis://localhost:6379/0
         with:

.ruby-version

@@ -1 +1 @@
-4.0.7
+4.0.9

Dockerfile

@@ -1,7 +1,7 @@
 # syntax = docker/dockerfile:1
 
 # Make sure it matches the Ruby version in .ruby-version and Gemfile
-ARG RUBY_VERSION=4.0.7
+ARG RUBY_VERSION=4.0.9
 FROM docker.io/library/ruby:$RUBY_VERSION-slim AS base
 
 # Rails app lives here

Dockerfile-export

@@ -1,7 +1,7 @@
 # syntax = docker/dockerfile:1
 
 # Make sure it matches the Ruby version in .ruby-version and Gemfile
-ARG RUBY_VERSION=4.0.7
+ARG RUBY_VERSION=4.0.9
 FROM ruby:$RUBY_VERSION-slim as base
 
 # Install the tools we need