Fix System Management tab rendering and profile avatar display issues

[ehsanking]

Motivation

• Fix blank/missing UI in the System Management (admin) area where reports and data tabs fell through to a generic placeholder.
• Prevent rendering failures for avatars stored as data URIs which were passed to next/image and could fail to render.

Description

• Add a small helper isDataUri and use it to render a safe <img> fallback for data: profile photo URLs while keeping next/image for normal remote URLs, applied to profile surfaces in app/chat/profile/page.tsx and multiple avatar spots in app/chat/ChatDashboardClient.tsx.
• Add explicit UI for the admin reports tab (list pending reports, Mark Resolved / Dismiss) and the data tab (system data export button) and wire them to existing admin actions resolveReport and exportSystemData.
• Remove a now-stale eslint-disable for an unused-vars warning to keep linting strict; keep all changes minimal and preserve existing auth/admin action flows and checks.

Testing

• Ran npm run lint and fixed a single warning; lint completed successfully.
• Ran npm run build and completed a full production build; build succeeded and route generation completed.
• No runtime/browser screenshots available in this environment; recommend manual smoke-check of the Profile page and Admin -> System Management (Reports and Data) in a browser after deployment.

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Codex Task