fix(GRO-693): add UAT Terraform infrastructure with correct GitRepository

- Add terraform workspace at apps/overlays/uat/terraform/ (backend.tf,
  main.tf, variables.tf, users.tf, imports.tf, terraform.tfvars)
- Add Terraform CRD (authentik-terraform.yaml) with correct path
  ./apps/overlays/uat/terraform relative to groombook/app repo root
- Add GitRepository CRD (gitrepository-groombook.yaml) pointing to
  groombook/app at fix/gro-844-network-policy branch (NOT groombook/infra
  which no longer exists)
- Add kustomization.yaml to tie it together

Root cause: the GitRepository was pointing to https://github.com/groombook/infra
which no longer exists, and the terraform files were not committed to the
current repository at the correct path.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/overlays/uat/terraform/imports.tf

@@ -0,0 +1,12 @@
+# Import existing Authentik resources into Terraform state.
+# These blocks are consumed on the first apply and become no-ops thereafter.
+
+import {
+  to = authentik_oauth2_provider.groombook-uat
+  id = "284"
+}
+
+import {
+  to = authentik_application.groombook-uat
+  id = "e77a9c45-bed6-4a23-bc62-178f166f099e"
+}