Add GitLab Redis initializer ordering fix

Fixes NameError: uninitialized constant Gitlab::Redis::ALL_CLASSES
caused by 7_prometheus_metrics.rb loading before 7_redis.rb
(alphabetically 'p' < 'r'). The ConfigMap provides a 0_redis_early.rb
initializer that requires gitlab/redis before other initializers run.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/gitlab/manifests/redis-init-fix.yaml

@@ -0,0 +1,12 @@
+# Fix for GitLab initializer ordering bug:
+# 7_prometheus_metrics.rb loads before 7_redis.rb (alphabetical 'p' < 'r'),
+# triggering Redis cache access before Gitlab::Redis::ALL_CLASSES is defined.
+# This ConfigMap provides an early initializer that loads the Redis module first.
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: redis-init-fix
+  namespace: gitlab
+data:
+  0_redis_early.rb: |
+    require "gitlab/redis"