fix(crypto): align server-side encrypted format with client-side Web Crypto API

The server-side encrypt function in crypto-server.ts used format
`iv + authTag + encrypted`, but the client-side decrypt function in
crypto.ts expects `iv + encrypted + authTag` (authTag at the end,
matching Web Crypto API convention where ciphertext includes authTag).

This mismatch caused all admin API requests to fail with
"The operation failed for an operation-specific reason" when
NEXT_PUBLIC_ENCRYPTION_SECRET was configured, since the client
could not decrypt the server's response.

Fix: swap the order of authTag and encrypted in both encrypt and
decrypt functions in crypto-server.ts.

src/lib/crypto-server.ts

@@ -53,8 +53,9 @@ export function encrypt(plaintext: string): string {
   ]);
   const authTag = cipher.getAuthTag();
 
-  // 格式: iv + authTag + encrypted
-  const combined = Buffer.concat([iv, authTag, encrypted]);
+  // 格式: iv + encrypted + authTag
+  // 与客户端 crypto.ts 的 decrypt 格式一致（Web Crypto API 将 authTag 附在 ciphertext 末尾）
+  const combined = Buffer.concat([iv, encrypted, authTag]);
   return combined.toString('base64');
 }
 
@@ -66,8 +67,8 @@ export function decrypt(encryptedBase64: string): string {
   const combined = Buffer.from(encryptedBase64, 'base64');
 
   const iv = combined.subarray(0, IV_LENGTH);
-  const authTag = combined.subarray(IV_LENGTH, IV_LENGTH + AUTH_TAG_LENGTH);
-  const encrypted = combined.subarray(IV_LENGTH + AUTH_TAG_LENGTH);
+  const authTag = combined.subarray(combined.length - AUTH_TAG_LENGTH);
+  const encrypted = combined.subarray(IV_LENGTH, combined.length - AUTH_TAG_LENGTH);
 
   const decipher = crypto.createDecipheriv(ALGORITHM, key, iv);
   decipher.setAuthTag(authTag);