docs: replace enterprise-base image references with example-base (#27025)

Follow-up to #27018, sweeping the remaining
`codercom/enterprise-base:ubuntu` references to
`codercom/example-base:ubuntu` and `coder/enterprise-images` links to
[coder/images](https://github.com/coder/images). The `example-` prefix
is the recommended one for new deployments per the coder/images README.

Covers the 11 docs pages flagged by doc-check on #27018 plus the
embedded `examples/templates/docker` and `examples/templates/kubernetes`
starter templates (image string only; the `image` variable lives in the
coder/registry templates, see coder/registry#943).

OpenShift imagestream names in `docs/install/openshift.md` keep the
`enterprise-base` local name; only the upstream image reference changed.

Part of DEVREL-201.

🤖 Generated with Coder Agents using Claude, on behalf of @bpmct

examples/templates/docker/main.tf

@@ -173,7 +173,7 @@ resource "docker_volume" "home_volume" {
 
 resource "docker_container" "workspace" {
   count = data.coder_workspace.me.start_count
-  image = "codercom/enterprise-base:ubuntu"
+  image = "codercom/example-base:ubuntu"
   # Uses lower() to avoid Docker restriction on container names.
   name = "coder-${data.coder_workspace_owner.me.name}-${lower(data.coder_workspace.me.name)}"
   # Hostname makes the shell more user friendly: coder@my-workspace:~$

examples/templates/kubernetes/README.md

@@ -19,7 +19,7 @@ Provision Kubernetes Pods as [Coder workspaces](https://coder.com/docs/user-guid
 
 **Cluster**: This template requires an existing Kubernetes cluster
 
-**Container Image**: This template uses the [codercom/enterprise-base:ubuntu image](https://github.com/coder/enterprise-images/tree/main/images/base) with some dev tools preinstalled. To add additional tools, extend this image or build it yourself.
+**Container Image**: This template uses the [codercom/example-base:ubuntu image](https://github.com/coder/images/tree/main/images/base) with some dev tools preinstalled. To add additional tools, extend this image or build it yourself.
 
 ### Authentication
 

examples/templates/kubernetes/main.tf

@@ -285,7 +285,7 @@ resource "kubernetes_deployment_v1" "main" {
 
         container {
           name              = "dev"
-          image             = "codercom/enterprise-base:ubuntu"
+          image             = "codercom/example-base:ubuntu"
           image_pull_policy = "Always"
           command           = ["sh", "-c", coder_agent.main.init_script]
           security_context {