fix: add author email back for Linux deb/rpm packaging

electron-builder's Linux targets require author.email in package.json.
The field was accidentally removed when replacing email with URL.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 7418

package.json

@@ -9,6 +9,7 @@
   ],
   "author": {
     "name": "op7418",
+    "email": "guohao631@gmail.com",
     "url": "https://x.com/op7418"
   },
   "description": "A multi-model AI agent desktop client",