[Helper] Fix cold-standby script to support digits and override files (#6800)

This commit fixes two bugs in the cold-standby script:

1. Support digits in COMPOSE_PROJECT_NAME
   The script was stripping digits from COMPOSE_PROJECT_NAME, while
   backup_and_restore.sh (fixed in a71d991c) correctly supports them.
   Added '0-9' to the tr character set to align behavior.

2. Support docker-compose.override.yml on remote
   Lines 172 and 287 explicitly used '-f docker-compose.yml' which
   causes Docker Compose to ignore docker-compose.override.yml even
   when present. Changed to 'cd && compose' pattern (matching line 296)
   to auto-discover override files.

   Impact: Users with custom volumes/services in override file would
   experience silent failures - volumes not created, images not pulled,
   data syncing to wrong locations.

Both fixes ensure cold-standby works correctly with standard Docker
Compose conventions and user customizations.

Co-authored-by: Christophe Neuerburg <c.neuerburg@sdsys.ch>

helper-scripts/_cold-standby.sh

@@ -117,7 +117,7 @@ fi
 SCRIPT_DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
 source "${SCRIPT_DIR}/../mailcow.conf"
 COMPOSE_FILE="${SCRIPT_DIR}/../docker-compose.yml"
-CMPS_PRJ=$(echo ${COMPOSE_PROJECT_NAME} | tr -cd 'A-Za-z-_')
+CMPS_PRJ=$(echo ${COMPOSE_PROJECT_NAME} | tr -cd '0-9A-Za-z-_')
 SQLIMAGE=$(grep -iEo '(mysql|mariadb)\:.+' "${COMPOSE_FILE}")
 
 preflight_local_checks
@@ -169,7 +169,7 @@ if ! ssh -o StrictHostKeyChecking=no \
   -i "${REMOTE_SSH_KEY}" \
   ${REMOTE_SSH_HOST} \
   -p ${REMOTE_SSH_PORT} \
-  ${COMPOSE_COMMAND} -f "${SCRIPT_DIR}/../docker-compose.yml" create 2>&1 ; then
+  "cd \"${SCRIPT_DIR}/../\" && ${COMPOSE_COMMAND} create 2>&1" ; then
     >&2 echo -e "\e[31m[ERR]\e[0m - Could not create networks, volumes and containers on remote"
 fi
 
@@ -284,7 +284,7 @@ echo "OK"
     -i "${REMOTE_SSH_KEY}" \
     ${REMOTE_SSH_HOST} \
     -p ${REMOTE_SSH_PORT} \
-    ${COMPOSE_COMMAND} -f "${SCRIPT_DIR}/../docker-compose.yml" pull --quiet 2>&1 ; then
+    "cd \"${SCRIPT_DIR}/../\" && ${COMPOSE_COMMAND} pull --quiet 2>&1" ; then
       >&2 echo -e "\e[31m[ERR]\e[0m - Could not pull images on remote"
   fi