fix(ci): add prepare job, auto-version, fix Windows build issues

- Add prepare job: computes version (4.12.{run_number}), creates/updates
  the Gitea release once — eliminates the race condition where build-windows
  and build-linux both tried to create the same release simultaneously.
- Auto-increment version: both build jobs patch tauri.conf.json with
  4.12.{run_number} before building, so every CI run produces a strictly
  increasing semver and the Tauri updater fires correctly.
- Fix double -- in Windows build command: was 'build -- --bundles nsis'
  which passed --bundles as cargo args (silently ignored), causing all
  bundle targets to build. Now 'build --bundles nsis' (single --).
- Add setup-node to Windows build: pins Node.js to .node-version like
  the Linux job already does.
- update-manifest: uses version/release_id from prepare outputs instead
  of re-fetching and parsing the release name.
- Fix window title: was "Cinny", now "Lotus Chat".

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src-tauri/src/lib.rs

@@ -27,7 +27,7 @@ pub fn run() {
 
             let app_handle = app.handle().clone();
             let window = WebviewWindowBuilder::new(app, "main".to_string(), window_url)
-                .title("Cinny")
+                .title("Lotus Chat")
                 .disable_drag_drop_handler()
                 .on_new_window(move |url, _features| {
                     let _ = app_handle.opener().open_url(url.as_str(), None::<&str>);