Fix frontend TypeScript build errors

- Inline tsconfig.base.json settings into frontend/tsconfig.json (same
  Docker context issue as backend — only frontend/ is copied)
- Upgrade @types/react and @types/react-dom to ^19.0.0 to satisfy
  antd 5.20.x which references React.ActionDispatch (React 19 type);
  React 18 runtime is unchanged

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.env

@@ -0,0 +1,19 @@
+# PostgreSQL connection URL
+POSTGRES_URL=postgresql://mremotify:mremotify@localhost:5432/mremotify
+
+# AES-256 encryption key for passwords (must be exactly 32 characters)
+ENCRYPTION_KEY=change-me-to-a-random-32char-key!
+
+# JWT signing secret
+JWT_SECRET=c4baf6aca61629fcdf2285be2162e662ffec79a5db4e24d8bad2556f6f10c8c5
+
+# Default admin credentials (used during first-time seeding)
+ADMIN_USER=admin
+ADMIN_PASSWORD=admin123
+
+# Apache Guacamole daemon
+GUACD_HOST=guacd
+GUACD_PORT=4822
+
+# Backend port
+PORT=3000