[bug] v0.5.22 Windows build is broken — embedded frontend assets reference CI runner path

## Describe the bug

Buzz Desktop v0.5.22 for Windows (x64) fails to load the UI. The webview shows a Chromium `ERR_FILE_NOT_FOUND` error page instead of the app.

## Root cause

The embedded Tauri frontend assets reference a path from the GitHub Actions CI build environment instead of being bundled correctly. When the WebView2 tries to load the frontend, it navigates to:

```
file:///C:/Users/RUNNER~1/AppData/Local/Temp/buzz-tauri-package-assets-izi1rV/dist
```

This path only exists on the CI runner that built the release. On any end-user machine, the path doesn't exist, so WebView2 returns `ERR_FILE_NOT_FOUND`.

Evidence from `chrome_debug.log` with `WEBVIEW2_ADDITIONAL_BROWSER_ARGUMENTS="--enable-logging --v=1"`:

```
FileURLLoader::Start: file:///C:/Users/RUNNER~1/AppData/Local/Temp/buzz-tauri-package-assets-izi1rV/dist
```

The string `buzz-tauri-package-assets` is present in the `buzz-desktop.exe` binary (confirmed via binary search).

## Affected release

- **Version:** `Buzz_0.5.22_x64-setup_alpha-unsigned.exe` (desktop-v0.5.22)
- **SHA256:** `c76aa32e75faa20aee5d8cd1c1c2c00265bc94166c3cb6a88455a6819e9ec289` (installer)
- **Installed binary SHA256:** `820c04d78c8805ad8b4cb45e6a38a6329a5d70e21ff00bb98739815c4b0c5dcf`

## Not affected

- **v0.5.20** (`Buzz_0.5.20_x64-setup_alpha-unsigned.exe`) works correctly — the `buzz-tauri-package-assets` string is **not** present in that binary, and the app loads the UI normally.

## Steps to reproduce

1. Download `Buzz_0.5.22_x64-setup_alpha-unsigned.exe` from the desktop-v0.5.22 release
2. Install on a Windows machine (clean install or upgrade)
3. Launch `buzz-desktop.exe`
4. Observe: `ERR_FILE_NOT_FOUND` error page in the webview

## Expected behavior

The app UI should load normally, as it does on v0.5.20.

## Environment

- **OS:** Windows 11 (build 26200.9278)
- **WebView2:** 152.0.4191.62
- **Buzz:** v0.5.22 (broken), v0.5.20 (working)

## Likely fix

The Tauri build pipeline for the Windows x64 release may be using `tauri build --bundles nsis` with a development/debug asset configuration that resolves to a temp directory on the runner instead of embedding the frontend into the binary. The build step that packages `dist/` into the PE binary appears to have used the runner's filesystem path as the asset root rather than embedding the files.