feat: top-up modal, pause/resume tracker, activity timeline, admin metrics

[davedumto]

Summary

Bundles four assigned issues that all touch overlapping pieces (stream actions, the activity feed, and admin observability) into a single PR so the diff stays coherent.

• Replace prompt()/alert() in handleTopUp with proper TopUpModal #355 — Replace prompt()/alert() in handleTopUp with proper TopUpModal

  • frontend/src/components/Dashboard.tsx: removed the legacy prompt() flow and wired the row's "Add Funds" button to the existing TopUpModal, which calls sorobanTopUp via Freighter (toBaseUnits for amount conversion). Errors surface via toSorobanErrorMessage.

• Add pause and resume buttons to stream detail page #356 — Add pause and resume buttons to stream detail page

  • frontend/src/app/streams/[id]/page.tsx: pause and resume now drive a TransactionTracker (signing → submitted → confirmed/failed) instead of window.location.reload(). Failure state surfaces a retry that re-issues the correct action based on the current paused flag, and the page refetches the stream record after submission so SSE/state recover without a hard reload.

• [Frontend] Build activity page with full event history #424 — Build activity page with full event history

  • Frontend: frontend/src/app/activity/page.tsx now hits the configured NEXT_PUBLIC_API_URL, drops the !loading gate that was suppressing the initial fetch, prefers the server-provided hasMore, and resets to an empty list on error. frontend/src/components/dashboard/ActivityHistory.tsx renders each timeline entry's stream id as a <Link> to the detail page so the audit log is navigable. The CSV export, the empty state, and the load-more pagination already existed and are kept intact.
  • Backend: new GET /v1/events?address=&type=&limit=&offset=&page= route in backend/src/routes/v1/events.routes.ts returns { events, total, limit, offset, hasMore }. Type filter accepts a comma list; invalid filters 400. Pagination supports both offset (preferred) and page (1-based, falls back to offset = (page - 1) * limit). Capped at 200/page.

• [Backend] Add stream metrics endpoint #426 — Add stream metrics endpoint

  • backend/src/routes/v1/admin.routes.ts: kept the existing nested protocol-health response and added the snake_case summary the issue contract calls for (total_streams, active_streams, paused_streams, completed_streams, cancelled_streams, total_volume_streamed). total_volume_streamed sums withdrawnAmount as BigInt so i128 precision survives the JSON boundary. The handler is now wrapped in a 60-second MemoryCache (existing cache from lib/redis.ts) and emits X-Cache: HIT/MISS for visibility.

• Tests

  • backend/tests/integration/admin-metrics.test.ts: covers the response shape, large-i128 precision (sum of two values past Number.MAX_SAFE_INTEGER), the cache miss → set, and a cache hit that bypasses Prisma entirely.
  • backend/tests/integration/events-list.test.ts: covers the missing-address 400, the paged shape, the comma-separated type filter, the all-invalid type filter, and page → offset fallback.

closes #355
closes #356
closes #424
closes #426

Test plan

• vitest run tests/integration/admin-metrics.test.ts — 4/4 pass
• vitest run tests/integration/events-list.test.ts — 5/5 pass
• tsc --noEmit clean for the touched files (existing dashboard-view.tsx / vitest.config.ts errors are pre-existing on main)
• lint-staged ran via the pre-commit hook
• Manual smoke: dashboard "Add Funds" → modal → Freighter → balance refresh
• Manual smoke: stream detail Pause → tracker progresses signing → submitted → confirmed
• Manual smoke: /activity lists events, type filter narrows, "Load more" appends, stream id link navigates to /streams/[id]
• Manual smoke: GET /v1/admin/metrics returns snake_case summary; second call within 60s returns X-Cache: HIT

Notes

• I left the existing /v1/admin/metrics nested fields (streams, events, fees, sse, cache, indexer, uptime) in place so the operator console keeps working alongside the new top-level summary.
• frontend/src/components/Dashboard.tsx is currently unreferenced from any route, but Replace prompt()/alert() in handleTopUp with proper TopUpModal #355 explicitly named the file, so its handler is fixed regardless.