fix: update Keycloak configuration and Docker healthcheck improvements

- Enabled `directAccessGrants` for `frontend-client` in `meldestelle-realm.json` to support ROPC login flow.
- Strengthened admin credentials in realm configuration to meet password policy requirements.
- Upgraded Keycloak to `26.5.5` with updated Docker healthcheck logic:
  - Replaced `curl` with bash `/dev/tcp` for compatibility with `ubi9-micro` image.
  - Switched health endpoint from `/ready` to `/live` for single-node use.
  - Adjusted healthcheck timings (`start_period`, `timeout`, `interval`) for smoother startup.
- Removed deprecated v1 hostname parameter `KC_HOSTNAME_STRICT_HTTPS`.

Signed-off-by: Stefan Mogeritsch <stefan.mo.co@gmail.com>

config/docker/keycloak/Dockerfile

@@ -1,16 +1,18 @@
 # ===================================================================
 # Production-Ready Keycloak Dockerfile
 # ===================================================================
-# Based on: quay.io/keycloak/keycloak:26.4
+# Based on: quay.io/keycloak/keycloak:26.5.5
 # Features:
 # - Pre-built optimized image (faster startup)
 # - Security hardening
 # - Health monitoring
 # ===================================================================
-ARG KEYCLOAK_IMAGE_TAG
+ARG KEYCLOAK_IMAGE_TAG=26.5.5
 
 FROM quay.io/keycloak/keycloak:${KEYCLOAK_IMAGE_TAG}
 
+ARG KEYCLOAK_IMAGE_TAG=26.5.5
+
 LABEL maintainer="Meldestelle Development Team"
 LABEL description="Production-ready Keycloak for Meldestelle authentication"
 LABEL version="${KEYCLOAK_IMAGE_TAG}"

config/docker/keycloak/meldestelle-realm.json

@@ -239,7 +239,7 @@
       "protocol": "openid-connect",
       "standardFlowEnabled": true,
       "implicitFlowEnabled": false,
-      "directAccessGrantsEnabled": false,
+      "directAccessGrantsEnabled": true,
       "serviceAccountsEnabled": false,
       "authorizationServicesEnabled": false,
       "attributes": {
@@ -283,7 +283,7 @@
       "credentials": [
         {
           "type": "password",
-          "value": "password",
+          "value": "Admin#1234",
           "temporary": false
         }
       ],
@@ -395,4 +395,4 @@
     "clientSessionMaxLifespan": "0",
     "clientOfflineSessionIdleTimeout": "0"
   }
-}
+}