Fix MariaDB socket readiness race condition in ARM64 Docker builds

[Copilot]

On linux/arm64 (QEMU), mysql_install_db takes ~44 minutes to complete. The subsequent sleep 4 before connecting was insufficient for MariaDB's socket to become available, causing all ARM64 builds to fail with ERROR 2002 (HY000): Can't connect to local server through socket '/run/mysqld/mysqld.sock'.

Changes

• All Dockerfile.php*: Replace fixed sleep 4 with a poll loop that retries SELECT 1 every second until the socket is ready, with a 120-second hard timeout to prevent indefinite hangs on genuine failures.

# Before
RUN sh -c 'mysqld_safe --datadir=/var/lib/mysql &' && sleep 4 && mysql -u root -e "CREATE DATABASE wordpress"

# After
RUN sh -c 'mysqld_safe --datadir=/var/lib/mysql &' && i=0; until mysql -u root -e "SELECT 1" >/dev/null 2>&1; do sleep 1; i=$((i+1)); if [ "$i" -ge 120 ]; then exit 1; fi; done && mysql -u root -e "CREATE DATABASE wordpress"

Applied to all 7 Dockerfiles (php7.4 through php8.5).