Added

• Tasks: createdAt timestamp is now automatically recorded when a task is created. Shown as a read-only “Created” line in the task sidenav when editing.
• Milestones: completedAt date is now automatically set when a milestone’s status is changed to “completed” and cleared if the status is changed back. Displayed as a read-only “Completed” line in the milestone sidenav.
• Settings: “Hide completed milestones after N days” option mirrors the existing task hide setting. Completed milestones older than the configured threshold are filtered from the milestones view.
• Sidenav: fullscreen toggle button is now available in all sidenav panels. Clicking the expand icon switches the panel to full viewport width; preference is persisted in localStorage.