fix(slink,fleet): append APP_ENV/APP_SECRET to .env, use setup_mariadb_db

- slink: APP_ENV and APP_SECRET not present in .env.example, sed patterns
  never matched → Symfony defaulted to dev mode → WebProfilerBundle crash
  (not installed with --no-dev). Now appends APP_ENV=prod + APP_SECRET.
- fleet: use setup_mariadb_db helper instead of manual SQL, reference
  MARIADB_DB_PASS, depend on mariadb.service

install/fleet-install.sh

@@ -14,16 +14,7 @@ network_check
 update_os
 
 setup_mariadb
-
-msg_info "Setting up Database"
-FLEET_DB_PASS=$(openssl rand -base64 18 | tr -dc 'a-zA-Z0-9' | head -c 13)
-$STD mysql -u root <<EOSQL
-CREATE DATABASE fleet;
-CREATE USER 'fleet'@'localhost' IDENTIFIED BY '${FLEET_DB_PASS}';
-GRANT ALL PRIVILEGES ON fleet.* TO 'fleet'@'localhost';
-FLUSH PRIVILEGES;
-EOSQL
-msg_ok "Set up Database"
+MARIADB_DB_NAME="fleet" MARIADB_DB_USER="fleet" setup_mariadb_db
 
 fetch_and_deploy_gh_release "fleet" "fleetdm/fleet" "prebuild" "latest" "/opt/fleet" "fleet_v*_linux.tar.gz"
 
@@ -34,7 +25,7 @@ cat <<EOF >/opt/fleet/.env
 FLEET_MYSQL_ADDRESS=127.0.0.1:3306
 FLEET_MYSQL_DATABASE=fleet
 FLEET_MYSQL_USERNAME=fleet
-FLEET_MYSQL_PASSWORD=${FLEET_DB_PASS}
+FLEET_MYSQL_PASSWORD=${MARIADB_DB_PASS}
 FLEET_SERVER_ADDRESS=0.0.0.0:8080
 FLEET_SERVER_TLS=false
 FLEET_AUTH_JWT_KEY=${JWT_KEY}
@@ -51,8 +42,8 @@ msg_info "Creating Service"
 cat <<EOF >/etc/systemd/system/fleet.service
 [Unit]
 Description=Fleet
-After=network.target mysql.service
-Requires=mysql.service
+After=network.target mariadb.service
+Requires=mariadb.service
 
 [Service]
 Type=simple