redis, valkey, harbor: the redis_exporter sidecar is amd64-only, so it crash-loops on arm64 #4519

The redis exporter sidecar can't start on arm64 nodes. Three charts pin oliver006/redis_exporter:v1.55.0-alpine, and that tag is a single amd64 manifest. On arm64 the container exits with an exec format error, and the Redis pod stays at 1/2 ready.

The pin is in three places:

• packages/apps/redis/templates/redisfailover.yaml
• packages/apps/valkey/templates/valkeyfailover.yaml
• packages/system/harbor/templates/redis.yaml

The same release without the suffix is a multi-arch index with amd64, arm and arm64. So dropping -alpine fixes it, no version bump needed. I checked both tags with crane manifest. On an arm64 test cluster the Harbor Redis pod went to 2/2 after switching the image.

Related to #1961.