fix: Optimize flipping card animation backface and timing

src/lib/env.ts

@@ -11,6 +11,14 @@ const envSchema = z.object({
   REDIS_URL: z.string().optional(),
   IP_SALT: z.string().default('development-salt-change-in-production'),
   ENABLE_DEMO: z.string().default('false'),
+
+  // Cloudflare R2 (S3 Compatible)
+  R2_ACCOUNT_ID: z.string().optional(),
+  R2_ACCESS_KEY_ID: z.string().optional(),
+  R2_SECRET_ACCESS_KEY: z.string().optional(),
+  R2_BUCKET_NAME: z.string().default('qrmaster-menus'),
+  R2_PUBLIC_URL: z.string().optional(),
+  MAX_UPLOAD_SIZE: z.string().default('10485760'), // 10MB default
 });
 
 // During build, we might not have all env vars, so we'll use defaults