Miner dashboard: overview route (index.tsx) skeleton and chart adoption

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Context

Part of epic #6504's visual/ui-kit track. apps/loopover-miner-ui/src/routes/index.tsx renders every metric as a bare number in a <dd>/<span> (line 24) with plain-text loading state, despite packages/loopover-ui-kit/src/components/skeleton.tsx and chart.tsx shipping in the shared kit unused by this app.

Requirements

• Adopt Skeleton for the loading state of index.tsx's SummaryCards, matching the real card layout instead of plain text.
• Adopt the shared async-state primitives from the ui-kit-port child issue of this same epic (blocked on that issue landing first) instead of hand-rolling loading/error/empty JSX.
• Consider chart.tsx adoption if the overview page's metrics have a natural trend/sparkline representation — otherwise this is skeleton-only.

Deliverables

• index.tsx restyled with skeleton loading state
• Shared StateBoundary/LoadingState adopted instead of the hand-rolled 4-branch JSX
• Before/after screenshots

Test Coverage Requirements

99%+ Codecov patch coverage on every changed line and branch, plus a regression test for the new/changed behavior (note: apps/** UI code may fall outside the strict Codecov patch gate — check coverage.include — but a before/after screenshot table per this repo's UI-PR convention is still required for any visual change).

Expected Outcome

The overview route's loading state matches its real layout and shares the same async-state component every other restyled route uses.

Links & Resources

Epic: #6504. apps/loopover-miner-ui/src/routes/index.tsx:24, packages/loopover-ui-kit/src/components/skeleton.tsx, chart.tsx.

[linear-code]

JSO-4712

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Already done — via #6509. apps/loopover-miner-ui/src/routes/index.tsx already imports Skeleton/StateBoundary from @loopover/ui-kit; CardStatsSkeleton mirrors the real stat rows, and all three summary cards (OverviewRunsCard, OverviewPortfolioCard, OverviewClaimsCard) already wrap content in StateBoundary. Closing as already resolved.