Add LoginLink client component that captures current path via usePathname()
and passes it as returnTo query param. Update login page to read and
sanitize returnTo (open-redirect guard: must start with /, reject //).
Update LoginForm to redirect to returnTo after successful login. Wire
LandingPage CTA through LoginLink. Add returnTo redirect for already-
authed users hitting /login. Add return-URL to flappy page redirect.
Remove trailing blank line from (frontend) layout.
Wire CommandPalette/Provider into the frontend layout and add Cmd+K
hint in the SiteHeader. Register context-aware commands for banking,
helpdesk, mission RSVP, locker, shipments, and market pages.
Also removes the locker search's duplicate Cmd+K listener (now handled
globally), renames its button to 'Search Locker', and cleans up a
flappy page parenthetical.
