[Enhancement] Enrollment and purchase tabs on user detail

[techifydev1]

Two read-only tabs pulling the same APIs the learner dashboard uses (hooks/usePurchases.js, course enrollment patterns):

• Enrollments: course title linking to admin course detail, enrolled date, progress % if available
• Purchases: amount in USDC, tx hash (truncated, copyable, explorer link), status, date

Admins are read-only here; no refund/cancel actions live in this tab, those belong to the payments section.