feat: add auto-updater support with GitHub releases

- Configure Tauri updater plugin with Ed25519 signing
- Add GitHub Actions support for signed builds
- Set up GitHub releases as update endpoint
- Enable update checking in Settings modal

src-tauri/tauri.conf.json

@@ -43,7 +43,9 @@
   "plugins": {
     "updater": {
       "pubkey": "dW50cnVzdGVkIGNvbW1lbnQ6IG1pbmlzaWduIHB1YmxpYyBrZXk6IDRERTRCNEUxQUE3MDA4QTYKUldTbUNIQ3E0YlRrVFF2cnFVVE1jczlNZFlmemxXd0h6cTdibXRJWjBDSytQODdZOTYvR3d3d2oK",
-      "endpoints":["http://127.0.0.1:8080/latest.json"]
+      "endpoints": [
+        "https://github.com/jasonyoung/cc-switch/releases/latest/download/latest.json"
+      ]
     }
   }
 }