refactor: update build scripts and add new server preparation scripts

- Replaced JavaScript files with ES module versions for server preparation and setup scripts.
- Introduced `prepare-server.mjs` for bundling server with Electron, enhancing dependency management.
- Added `rebuild-server-natives.cjs` for rebuilding native modules during the Electron packaging process.
- Updated `setup-e2e-fixtures.mjs` to create necessary directories and files for Playwright tests.
- Adjusted `package.json` scripts to reflect changes in file extensions and improve build process clarity.

apps/ui/scripts/rebuild-server-natives.cjs

@@ -0,0 +1,66 @@
+#!/usr/bin/env node
+
+/**
+ * Electron-builder afterPack hook
+ * Rebuilds native modules in the server bundle for the target architecture
+ */
+
+const { exec } = require('child_process');
+const { promisify } = require('util');
+const path = require('path');
+
+const execAsync = promisify(exec);
+
+exports.default = async function(context) {
+  const { appOutDir, electronPlatformName, arch, packager } = context;
+  const electronVersion = packager.config.electronVersion;
+
+  // Convert arch to string if it's a number (electron-builder sometimes passes indices)
+  const archNames = ['ia32', 'x64', 'armv7l', 'arm64', 'universal'];
+  const archStr = typeof arch === 'number' ? archNames[arch] : arch;
+
+  console.log(`\n🔨 Rebuilding server native modules for ${electronPlatformName}-${archStr}...`);
+
+  // Path to server node_modules in the packaged app
+  let serverNodeModulesPath;
+  if (electronPlatformName === 'darwin') {
+    serverNodeModulesPath = path.join(
+      appOutDir,
+      `${packager.appInfo.productName}.app`,
+      'Contents',
+      'Resources',
+      'server',
+      'node_modules'
+    );
+  } else if (electronPlatformName === 'win32') {
+    serverNodeModulesPath = path.join(
+      appOutDir,
+      'resources',
+      'server',
+      'node_modules'
+    );
+  } else {
+    serverNodeModulesPath = path.join(
+      appOutDir,
+      'resources',
+      'server',
+      'node_modules'
+    );
+  }
+
+  try {
+    // Rebuild native modules for the target architecture
+    const rebuildCmd = `npx --yes @electron/rebuild --version=${electronVersion} --arch=${archStr} --force --module-dir="${serverNodeModulesPath}/.."`;
+
+    console.log(`   Command: ${rebuildCmd}`);
+
+    const { stdout, stderr } = await execAsync(rebuildCmd);
+    if (stdout) console.log(stdout);
+    if (stderr) console.error(stderr);
+
+    console.log(`✅ Server native modules rebuilt successfully for ${archStr}\n`);
+  } catch (error) {
+    console.error(`❌ Failed to rebuild server native modules:`, error.message);
+    // Don't fail the build, just warn
+  }
+};