feat(frontend): match user page default view to Razor

[Seme30]

Part of #789.

Problem

/users?id=2 (Maya Patel) has the same heading and nav on both hosts, but the default body is a different product surface.

Current gaps

• Both render You are viewing Patel, Maya's Profile.
• Both have Stars / Subscriptions / Groups / Run Analytics / Report Runs / Atlas History / Analytics.
• Razor opens a sortable run table (Name, Type, Runs, Last Run) with seeded rows such as Inpatient Length of Stay (2 runs).
• Next.js opens the analytics dashboard (6 runs, 1 user, 219s) plus a Top reports list.

Frontend / Razor references

• frontend/app/users/page.tsx
• web/Pages/Users/Index.cshtml

Definition of done

• The default tab/body on Next.js matches Razor for a seeded user.
• The seven nav targets still work.
• Frontend tests cover the default view.