fix: Remove missing icon references and fix batch syntax

- Remove icon references from package.json (assets folder is empty)
- Fix batch script syntax by replacing if/else blocks with goto labels
- Remove parentheses and colons that conflict with batch syntax

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

client/package.json

@@ -50,15 +50,12 @@
           "arch": ["x64"]
         }
       ],
-      "icon": "assets/icon.ico",
       "signAndEditExecutable": false
     },
     "nsis": {
       "oneClick": false,
       "allowToChangeInstallationDirectory": true,
       "artifactName": "${productName}-${version}-setup.${ext}",
-      "installerIcon": "assets/icon.ico",
-      "uninstallerIcon": "assets/icon.ico",
       "deleteAppDataOnUninstall": false
     },
     "mac": {
@@ -67,8 +64,7 @@
           "target": "dmg",
           "arch": ["x64", "arm64"]
         }
-      ],
-      "icon": "assets/icon.icns"
+      ]
     },
     "linux": {
       "target": [
@@ -76,8 +72,7 @@
           "target": "AppImage",
           "arch": ["x64"]
         }
-      ],
-      "icon": "assets/icon.png"
+      ]
     },
     "portable": {
       "artifactName": "${productName}-${version}-portable.${ext}",