Fix: Add .env.production with correct API_URL including /btpxpress path

The frontend now correctly points to https://api.lions.dev/btpxpress
instead of just https://api.lions.dev, which fixes the communication
issue between frontend and backend.

This file is needed at build-time because Next.js bakes NEXT_PUBLIC_*
variables into the bundle during the build process.

Fixes:
- Frontend can now call backend API endpoints correctly
- Resolves 404 errors when making API requests
- Works with Ingress rewrite-target configuration

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.env.production

@@ -0,0 +1,28 @@
+# Production environment configuration for BTP Xpress Frontend
+# This file is used during the Docker build process for production deployments
+
+# API Backend - Points to the backend via Ingress at api.lions.dev/btpxpress
+NEXT_PUBLIC_API_URL=https://api.lions.dev/btpxpress
+
+# Keycloak Configuration
+NEXT_PUBLIC_KEYCLOAK_URL=https://security.lions.dev
+NEXT_PUBLIC_KEYCLOAK_REALM=btpxpress
+NEXT_PUBLIC_KEYCLOAK_CLIENT_ID=btpxpress-frontend
+
+# Application
+NEXT_PUBLIC_APP_NAME=BTP Xpress
+NEXT_PUBLIC_APP_VERSION=1.0.0
+NEXT_PUBLIC_APP_DESCRIPTION=Plateforme de gestion BTP
+NEXT_PUBLIC_APP_ENV=production
+
+# Theme
+NEXT_PUBLIC_DEFAULT_THEME=blue
+NEXT_PUBLIC_DEFAULT_THEME_MODE=light
+
+# Security
+NEXT_PUBLIC_SESSION_TIMEOUT=1800
+NEXT_PUBLIC_SECURITY_STRICT_MODE=true
+NEXT_PUBLIC_ENABLE_CLIENT_VALIDATION=true
+
+# Debug - disabled in production
+NEXT_PUBLIC_DEBUG=false