[Backport release-1.0] [system] Fix Keycloak proxy configuration for v26.x (#2134)

# Description
Backport of #2125 to `release-1.0`.

packages/system/keycloak/templates/sts.yaml

@@ -82,8 +82,10 @@ spec:
               value: "ispn"
             - name: KC_CACHE_STACK
               value: "kubernetes"
-            - name: KC_PROXY
-              value: "edge"
+            - name: KC_PROXY_HEADERS
+              value: "xforwarded"
+            - name: KC_HTTP_ENABLED
+              value: "true"
             - name: KEYCLOAK_ADMIN
               value: admin
             - name: KEYCLOAK_ADMIN_PASSWORD