Implement fixes from test results

- Update Docker install to use curl method
- Rename ADMIN_PASSWORD to AUTHELIA_ADMIN_PASSWORD
- Fix Authelia password hash generation (remove grep, no quotes)
- Revert compose labels to single quotes
- Ensure users_database.yml has unquoted password placeholder

scripts/install-prerequisites.sh

@@ -139,7 +139,7 @@ system_setup() {
             log_info "Docker service is already running"
         fi
     else
-        curl -fsSL https://get.docker.com | sh
+        curl -fsSL https://get.docker.com -o get-docker.sh && sudo sh get-docker.sh
         usermod -aG docker "$ACTUAL_USER"
         NEEDS_LOGOUT=true
     fi