fix: add .env.production for DOS Chain self-hosted deployment

Without this file checked in, production builds lose all NEXT_PUBLIC
env vars when /tmp is cleaned or Docker rebuilds from scratch.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: JOY

apps/web/.env.production

@@ -0,0 +1,9 @@
+NEXT_PUBLIC_WC_PROJECT_ID=4b6b77d337588564379b0ef8f3a5c479
+NEXT_PUBLIC_GATEWAY_URL_PRODUCTION=https://safe.doschain.com/cgw
+NEXT_PUBLIC_DEFAULT_MAINNET_CHAIN_ID=7979
+NEXT_PUBLIC_IS_OFFICIAL_HOST=false
+NEXT_PUBLIC_IS_PRODUCTION=true
+NEXT_PUBLIC_SAFE_VERSION=1.4.1
+NEXT_PUBLIC_BRAND_NAME=Safe on DOS
+NEXT_PUBLIC_BRAND_LOGO=/images/dos-logo.svg
+NEXT_PUBLIC_APP_HOMEPAGE=https://safe.doschain.com