fix: differentiate UNIQUE constraint from other DB errors on registration

Previously the catch block treated all insert errors as "username already
exists". Now it checks the error message for UNIQUE/SQLITE_CONSTRAINT and
only returns the duplicate-username message for that case. Other errors
are logged and return a generic failure message.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

server/api/auth/register.post.ts

@@ -2,8 +2,10 @@ import { registerSchema } from '../../utils/auth/validation'
 import { verifyCaptcha } from '../../utils/auth/captcha'
 import { dbGlobal } from 'drizzle-pkg/lib/db'
 import { users } from 'drizzle-pkg/lib/schema/auth'
-
 import { hash } from 'bcryptjs'
+import log4js from 'logger'
+
+const logger = log4js.getLogger('AUTH')
 
 export default defineWrappedResponseHandler(async (event) => {
   const body = await readBody(event)
@@ -33,7 +35,12 @@ export default defineWrappedResponseHandler(async (event) => {
       .returning({ id: users.id })
 
     return R.success({ id: result[0].id, username })
-  } catch {
+  } catch (err: any) {
+    const msg = String(err?.message ?? '')
+    if (msg.toLowerCase().includes('unique') || msg.includes('SQLITE_CONSTRAINT')) {
       return R.error('用户名已存在', null)
     }
+    logger.error('Failed to insert user', msg)
+    return R.error('注册失败，请稍后重试', null)
+  }
 })