Fix Dockerfile Ruby version to match Gemfile and .ruby-version

Update Ruby version in Dockerfile from 3.4.6 to 3.4.3 to match the
version specified in both Gemfile and .ruby-version files. This resolves
the Docker build failure where bundler was complaining about the Ruby
version mismatch.

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

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

Author: justin808

.controlplane/Dockerfile

@@ -1,5 +1,5 @@
 # Make sure RUBY_VERSION matches the Ruby version in .ruby-version and Gemfile
-ARG RUBY_VERSION=3.4.6
+ARG RUBY_VERSION=3.4.3
 FROM registry.docker.com/library/ruby:$RUBY_VERSION-slim as base
 
 # Current commit hash environment variable