refactor: split main file into smaller modules for better maintainability

backend/managers/butlerManager.js

@@ -0,0 +1,75 @@
+const fs = require('fs');
+const path = require('path');
+const AdmZip = require('adm-zip');
+const { TOOLS_DIR } = require('../core/paths');
+const { getOS, getArch } = require('../utils/platformUtils');
+const { downloadFile } = require('../utils/fileManager');
+
+async function installButler(toolsDir = TOOLS_DIR) {
+  if (!fs.existsSync(toolsDir)) {
+    fs.mkdirSync(toolsDir, { recursive: true });
+  }
+  
+  const butlerName = process.platform === 'win32' ? 'butler.exe' : 'butler';
+  const butlerPath = path.join(toolsDir, butlerName);
+  const zipPath = path.join(toolsDir, 'butler.zip');
+
+  if (fs.existsSync(butlerPath)) {
+    return butlerPath;
+  }
+
+  let urls = [];
+  const osName = getOS();
+  const arch = getArch();
+  if (osName === 'windows') {
+    urls = ['https://broth.itch.zone/butler/windows-amd64/LATEST/archive/default'];
+  } else if (osName === 'darwin') {
+    if (arch === 'arm64') {
+      urls = [
+        'https://broth.itch.zone/butler/darwin-arm64/LATEST/archive/default',
+        'https://broth.itch.zone/butler/darwin-amd64/LATEST/archive/default'
+      ];
+    } else {
+      urls = ['https://broth.itch.zone/butler/darwin-amd64/LATEST/archive/default'];
+    }
+  } else if (osName === 'linux') {
+    urls = ['https://broth.itch.zone/butler/linux-amd64/LATEST/archive/default'];
+  } else {
+    throw new Error('Operating system not supported');
+  }
+
+  console.log('Fetching Butler tool...');
+  let lastError = null;
+  for (const url of urls) {
+    try {
+      await downloadFile(url, zipPath);
+      lastError = null;
+      break;
+    } catch (error) {
+      lastError = error;
+    }
+  }
+  if (lastError) {
+    throw lastError;
+  }
+
+  console.log('Unpacking Butler...');
+  const zip = new AdmZip(zipPath);
+  zip.extractAllTo(toolsDir, true);
+
+  if (process.platform !== 'win32') {
+    fs.chmodSync(butlerPath, 0o755);
+  }
+
+  try {
+    fs.unlinkSync(zipPath);
+  } catch (err) {
+    console.log('Notice: could not delete butler.zip');
+  }
+
+  return butlerPath;
+}
+
+module.exports = {
+  installButler
+};