[FE-36] Build /admin/audit-logs page — HTTP access log viewer with user and date filters

[mftee]

Overview

Administrators need to review HTTP access logs for security investigations and compliance audits. Once the backend records access logs (BE-06) and exposes them via GET /api/audit (BE-68), this page provides the interface.

Background

File to create: frontend/app/(protected)/admin/audit-logs/page.tsx

Access: Admin role only

Features:

• Paginated table of audit log entries from GET /api/audit
• Columns: Actor name/email, Action, Target type + ID, IP address, Timestamp
• Filters:
  • User filter (search by email)
  • Action type dropdown
  • Date range picker
• Click a row to expand: show full JSON metadata in a code block
• "Export CSV" button (calls GET /api/audit?format=csv)

Acceptance Criteria

• Table loads audit logs in reverse chronological order
• Date range filter uses a date picker with start and end inputs
• Row expansion shows the full metadata payload
• CSV export triggers a file download
• Table handles empty state when no logs match the filters