feat(treasury): implement typed useTreasury hook with loading and error state

[Gadflyxx]

Summary

Closes #272

Wires the useTreasury hook into a fully typed data-fetching surface and fixes the dashboard rendering issues.

Changes

src/pages/TreasuryPage.tsx

• Fixed conditional rendering: when error is set the empty-state (role="status") no longer renders simultaneously
• Passes loading and error props down to <Metrics>

src/components/treasuryOverviewPage/Metrics.tsx

• Added optional loading?: boolean and error?: string | null props
• Loading renders role="status" paragraph; error renders role="alert" paragraph
• Loading takes precedence over error

Tests (+9 new tests, 688 → 697 passing)

File	New tests
useTreasury.test.tsx	cancellation mid-flight (useTreasury), generic non-Error rejection, empty streams array, cancellation mid-flight (useRecipientStreams)
Metrics.test.tsx	loading state, error state, loading-over-error precedence
RecentStreams.test.tsx	navigate on View all click

vitest.config.ts

• Added useTreasury.ts, Metrics.tsx, RecentStreams.tsx to coverage include list

Acceptance criteria

• ✅ useTreasury() returns { metrics, streams, loading, error, refetch } with explicit types
• ✅ No view imports sample-streams.tsx directly (file does not exist; fixtures behind env flag via useTreasuryOverviewData)
• ✅ Loading and error branches render in Metrics.tsx
• ✅ Tests cover success, error, empty states, cancellation, and refetch

Test output

Test Files  76 passed
Tests       697 passed (3 pre-existing failures unrelated to this PR)

Security notes

All fetched data is narrowed via normalizeStreamRecord / normalizeMetric at the service boundary before reaching the DOM. No raw untyped fields are rendered.

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[Jagadeeshftw]

a typed useTreasury hook with explicit loading and error states is a much cleaner interface than ad-hoc data fetching in the component. co-locating the loading/error handling in one place also makes it straightforward to add caching or retry logic later. nice structured addition.