feat: restructure feature management and update project files

- Introduced a new `package-lock.json` to manage dependencies.
- Removed obsolete `.automaker/feature_list.json` and replaced it with a new structure under `.automaker/features/{id}/feature.json` for better organization.
- Updated various components to utilize the new features API for managing features, including creation, updates, and deletions.
- Enhanced the UI to reflect changes in feature management, including updates to the sidebar and board view.
- Improved documentation and comments throughout the codebase to clarify the new feature management process.

app/electron/services/worktree-manager.js

@@ -176,15 +176,8 @@ class WorktreeManager {
       try {
         await fs.mkdir(automakerDst, { recursive: true });
 
-        // Copy feature_list.json
-        const featureListSrc = path.join(automakerSrc, "feature_list.json");
-        const featureListDst = path.join(automakerDst, "feature_list.json");
-        try {
-          const content = await fs.readFile(featureListSrc, "utf-8");
-          await fs.writeFile(featureListDst, content, "utf-8");
-        } catch {
-          // Feature list might not exist yet
-        }
+        // Note: Features are stored in .automaker/features/{id}/feature.json
+        // These are managed by the main project, not copied to worktrees
 
         // Copy app_spec.txt if it exists
         const appSpecSrc = path.join(automakerSrc, "app_spec.txt");