Fix sidecar not found on Windows/macOS/Linux: switch from externalBin to resources

Tauri's externalBin only bundled the single sidecar executable, but
PyInstaller's onedir output requires companion DLLs and _internal/.
The binary was also renamed with a target triple suffix that
resolve_sidecar_path() didn't look for, causing it to fall back to
dev mode which used a compile-time CI path (CARGO_MANIFEST_DIR).

- Switch from externalBin to bundle.resources to include all sidecar files
- Pass Tauri resource_dir to sidecar manager for platform-aware path resolution
- Remove rename_binary() since externalBin target triple naming is no longer needed
- Remove broken production-to-dev fallback that could never work on user machines

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

src-tauri/src/lib.rs

@@ -27,6 +27,11 @@ pub fn run() {
         .plugin(tauri_plugin_dialog::init())
         .manage(app_state)
         .setup(|app| {
+            // Tell the sidecar manager where Tauri placed bundled resources
+            if let Ok(resource_dir) = app.path().resource_dir() {
+                sidecar::init_resource_dir(resource_dir);
+            }
+
             // Set the webview background to match the app's dark theme
             if let Some(window) = app.get_webview_window("main") {
                 let _ = window.set_background_color(Some(Color(10, 10, 35, 255)));