fix(tauri): sync native app version with package releases (#257)

## Summary
- sync the Tauri native version metadata from
`packages/tauri-app/package.json` so release builds pick up workspace
version bumps like `0.13.1`
- update the checked-in Tauri `Cargo.toml` and `tauri.conf.json`
versions from `0.12.3` to `0.13.1`
- document the prebuild sync behavior in `BUILD.md`

## Testing
- `node packages/tauri-app/scripts/sync-tauri-version.js`

packages/tauri-app/package.json

@@ -8,6 +8,7 @@
     "dev:ui": "npm run dev --workspace @codenomad/ui",
     "dev:prep": "node ./scripts/dev-prep.js",
     "dev:bootstrap": "npm run dev:prep && npm run dev:ui",
+    "sync:version": "node ./scripts/sync-tauri-version.js",
     "prebuild": "node ./scripts/prebuild.js",
     "bundle:server": "npm run prebuild",
     "build": "tauri build"