fix(promoter): correct Forgejo registry service hostname

forgejo-gitea-http.cicd.svc.cluster.local (headless svc, port 3000)
not forgejo-gitea (doesn't exist). Also wire REGISTRY_BASE env var
in deployment.yaml so it can be overridden without code change.

internal/webhook/promoter.go

@@ -224,10 +224,15 @@ func (p *ImagePromoter) patchApplication(ctx context.Context, entry promotionEnt
 	case "kustomize":
 		images := getKustomizeImages(app, entry.SourceIndex)
 		newImages := updateImageEntry(images, image, digest)
-		path := fmt.Sprintf("/spec/sources/%d/kustomize/images", entry.SourceIndex)
+		// Patch the full kustomize block (not just /kustomize/images) so the
-		patch = []map[string]any{
+		// op succeeds even when the kustomize key is absent from the source.
-			{"op": "add", "path": path, "value": newImages},
+		// These apps only use kustomize overrides for image pinning, so
-		}
+		// replacing the whole block is safe.
+		patch = []map[string]any{{
+			"op":    "add",
+			"path":  fmt.Sprintf("/spec/sources/%d/kustomize", entry.SourceIndex),
+			"value": map[string]any{"images": newImages},
+		}}
 
 	case "helm":
 		// Helm runners use spec.source (singular). Patch helm parameters