Feature/dashboard page

[dcl10]

Description

Implement the dashboard page at /dashboard, replacing the current stub. The dashboard is the post-login landing page and should work for both project managers and team members.

Two sections:

• Pending invitations — surfaces any Invited or Requested memberships using the existing InvitationCard component
• My projects — split into "Managing" (projects created by the user) and "Member of" (accepted team memberships), with an empty state when neither apply

The dashboard also needs a layout wrapping it in the AppShell (TopBar + LeftRail), which it currently lacks.

Tasks

• Add app/dashboard/layout.tsx mirroring the projects layout (auth guard + AppShell)
• Fetch currentUser, memberships, and projects in parallel in the page
• Render pending invitations section using InvitationCard
• Render "Managing" subsection using ProjectCard for projects created by the current user
• Render "Member of" subsection as simple rows (title + role + status pill) for accepted memberships
• Render EmptyState when the user has no projects or memberships