Fix critical shellcheck issues in selenium component scripts

Address only the most critical shellcheck issues without excessive quoting:
- Add missing shebangs to 3 files (devkeycloak-proxy, forward-proxy, proxy)
- Replace legacy backtick syntax with modern $() in 2 files
- Remove unused SCRIPT variable in rabbitmq

These changes improve script portability and maintainability while keeping
the existing coding style. Remaining SC2086 (quoting) warnings are
informational and left as-is per project preference.

Author: Zerpet

selenium/bin/components/devkeycloak-proxy

@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 HTTPD_DOCKER_IMAGE=${HTTPD_DOCKER_IMAGE:-httpd:latest}
 
 ensure_devkeycloak-proxy() {

selenium/bin/components/forward-proxy

@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 HTTPD_DOCKER_IMAGE=${HTTPD_DOCKER_IMAGE:-httpd:latest}
 
 ensure_forward-proxy() {

selenium/bin/components/other-rabbitmq

@@ -69,7 +69,7 @@ start_local_other_rabbitmq() {
 
   print "> EFFECTIVE RABBITMQ_CONFIG_FILE: /tmp/other$MOUNT_RABBITMQ_CONF"
   cp ${RABBITMQ_CONFIG_DIR}/enabled_plugins /tmp/other/etc/rabbitmq/
-  RABBITMQ_ENABLED_PLUGINS=`cat /tmp/other/etc/rabbitmq/enabled_plugins | tr -d " \t\n\r" | awk -F'[][]' '{print $2}'`
+  RABBITMQ_ENABLED_PLUGINS=$(cat /tmp/other/etc/rabbitmq/enabled_plugins | tr -d " \t\n\r" | awk -F'[][]' '{print $2}')
   print "> EFFECTIVE PLUGINS: $RABBITMQ_ENABLED_PLUGINS"
 
   ${BIN_DIR}/gen-advanced-config "${PROFILES_FOR_OTHER}" ${RABBITMQ_CONFIG_DIR} $OTHER_ENV_FILE /tmp/other$MOUNT_ADVANCED_CONFIG

selenium/bin/components/proxy

@@ -1,3 +1,5 @@
+#!/usr/bin/env bash
+
 HTTPD_DOCKER_IMAGE=${HTTPD_DOCKER_IMAGE:-httpd:latest}
 
 ensure_proxy() {

selenium/bin/components/rabbitmq

@@ -1,7 +1,5 @@
 #!/usr/bin/env bash
 
-SCRIPT="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-
 
 init_rabbitmq() {
   RABBITMQ_CONFIG_DIR=${TEST_CONFIG_DIR}
@@ -70,7 +68,7 @@ start_local_rabbitmq() {
 
   print "> EFFECTIVE RABBITMQ_CONFIG_FILE: /tmp$MOUNT_RABBITMQ_CONF"
   cp ${RABBITMQ_CONFIG_DIR}/enabled_plugins /tmp/etc/rabbitmq/
-  RABBITMQ_ENABLED_PLUGINS=`cat /tmp/etc/rabbitmq/enabled_plugins | tr -d " \t\n\r" | awk -F'[][]' '{print $2}'`
+  RABBITMQ_ENABLED_PLUGINS=$(cat /tmp/etc/rabbitmq/enabled_plugins | tr -d " \t\n\r" | awk -F'[][]' '{print $2}')
   print "> EFFECTIVE PLUGINS: $RABBITMQ_ENABLED_PLUGINS"
 
   ${BIN_DIR}/gen-advanced-config "${PROFILES}" ${RABBITMQ_CONFIG_DIR} $ENV_FILE /tmp$MOUNT_ADVANCED_CONFIG