fix: enable cipher key encryption feature for 2026.4.x clients and streamline key handling

src/config/limits.ts

@@ -149,9 +149,10 @@
     // Single source of truth for /config.version and /api/version.
     // /config.version 与 /api/version 的统一版本号来源。
     bitwardenServerVersion: '2026.4.1',
-    // Advertise official per-cipher item-key encryption support only after
-    // NodeWarden can guarantee key/field consistency across all write paths.
-    // 在所有写入路径都能保证 cipher.key 与字段密文一致之前，不向官方客户端声明支持逐项密钥加密。
-    cipherKeyEncryptionFeatureEnabled: false,
+    // Official 2026.4.x clients need this flag to receive and use cipher.key.
+    // Hiding existing item keys makes item-key encrypted vault data unreadable.
+    // 官方 2026.4.x 客户端需要该开关来接收并使用 cipher.key。
+    // 隐藏已有逐项密钥会导致逐项密钥加密的密码库数据无法解密。
+    cipherKeyEncryptionFeatureEnabled: true,
   },
 } as const;