feat(feature-list-protection): implement multi-layered protection strategy for feature list

- Removed the `FEATURE_LIST_PROTECTION.md` documentation file as the protection strategy has been fully implemented.
- Updated the `.automaker/feature_list.json` to an empty array to prevent accidental data loss.
- Enhanced the context management and prompt generation to include critical warnings and memory content for agents.
- Added validation, auto-backup, and access control mechanisms to safeguard the feature list from direct modifications.

These changes ensure robust protection against data loss and improve the overall safety of feature management within the application.

app/src/components/layout/sidebar.tsx

@@ -699,7 +699,7 @@ export function Sidebar() {
             </button>
             <button
               onClick={() => setShowTrashDialog(true)}
-              className="group flex items-center justify-center px-3 py-2.5 rounded-lg relative overflow-hidden transition-all text-muted-foreground hover:text-primary hover:bg-destructive/10 border border-sidebar-border"
+              className="group flex items-center justify-center px-3 h-[42px] rounded-lg relative overflow-hidden transition-all text-muted-foreground hover:text-primary hover:bg-destructive/10 border border-sidebar-border"
               title="Trash"
               data-testid="trash-button"
             >
@@ -778,7 +778,7 @@ export function Sidebar() {
               <DropdownMenu>
                 <DropdownMenuTrigger asChild>
                   <button
-                    className="hidden lg:flex items-center justify-center w-8 h-8 rounded-lg text-muted-foreground hover:text-foreground hover:bg-sidebar-accent/50 border border-sidebar-border transition-all titlebar-no-drag"
+                    className="hidden lg:flex items-center justify-center w-8 h-[42px] rounded-lg text-muted-foreground hover:text-foreground hover:bg-sidebar-accent/50 border border-sidebar-border transition-all titlebar-no-drag"
                     title="Project history"
                     data-testid="project-history-menu"
                   >