Feature Request: Allow project admins to set a default sidebar for all team members

Feature request

Is your feature request related to a problem?

• PostHog's sidebar shortcuts are currently configured per individual user. There is no way for a project admin or organization owner to define a default sidebar layout that is applied to all members of a project or organization when they first log in.
• New team members joining a PostHog project start with a generic sidebar, requiring each person to manually pin the relevant products, dashboards, insights, and folders that are important to the team. This is especially painful for larger teams or organizations that onboard members frequently.

Describe the solution you'd like

• It would be great to have an admin-level setting where you can specify which apps, dashboards, etc. are automatically pinned for new users.
• Ideally, admins should also have the option to push an updated default sidebar to all existing members, with a clear prompt that allows individuals to accept or dismiss the update to preserve personal customizations.

Describe alternatives you've considered

• Right now users have to manually add their own shortcuts, which can lead to disparate experiences.

Additional context

• From https://posthoghelp.zendesk.com/agent/tickets/56107 (moved to PostHog: https://us.posthog.com/project/2/support/tickets/56928)

Debug info

Session: https://us.posthog.com/project/sTMFPsFhdP1Ssg/replay/019d9d7d-2090-76f7-95cd-2b649ea28a7c?t=1792
Admin: http://go/adminOrgUS/019c4ed6-add0-0000-998a-30c999608349 (project ID 311650)

Start by locating the existing per-user sidebar shortcut settings and the project or organization admin settings. Define the behavior for applying defaults to new members and for prompting existing members before changing personal customizations; done means both flows are implemented with appropriate admin controls.