feat: add cross-platform release automation

Add a GitHub Actions workflow that validates the app on pushes and pull requests, and publishes Windows, macOS, and Linux release assets when a tag is pushed.

Also replace the Windows-only packaging flow with cross-platform Bun scripts for sidecar publishing and Electron packaging so the release job can package each runner natively.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

tsconfig.json

@@ -28,6 +28,7 @@
   },
   "include": [
     "electron.vite.config.ts",
+    "scripts/**/*.ts",
     "src/**/*.ts",
     "src/**/*.tsx",
     "tests/**/*.ts"