Add dashboard error boundaries

[jfust3]

Summary

Adds reusable React error boundaries around the dashboard surface and stat-card grid so a render failure in one dynamic UI section does not blank the whole app.

Closes #1.

Changes

• Adds frontend/src/components/ErrorBoundary.tsx with typed React error-boundary state, retry handling, accessible fallback UI, and telemetry/local error reporting.
• Wraps the main Dashboard panel in a section-level boundary.
• Wraps the stat-card grid in a separate card-level boundary so dashboard panels remain usable if a stat card fails.
• Keeps raw stack traces out of the user-facing fallback while preserving developer diagnostics through telemetry and console.error.

Testing

• npm install — completed, 0 vulnerabilities
• npm run build — passed (tsc -b && vite build)
• python3 build.py — completed diagnostics and produced diagnostic/build-94e0fb08.logd plus diagnostic/build-94e0fb08.json; frontend, market, and v2-market-stream passed, while unrelated modules failed because this runner lacks cargo/cmake/JRE/luac/ghc and frailbox has an existing C warning/error.
• git diff --check — passed

Diagnostic log password:

553deb0a337969a67bea

Checklist

• Relevant modules affected by these changes build locally
• Tests pass locally
• Diagnostic build log is committed in this PR
• Documentation has been updated, if applicable
• Configuration or schema changes are documented, if applicable
• No generated build artifacts are committed, except the required diagnostic build log
• Changes are scoped to the PR purpose and avoid unrelated cleanup
• Security, privacy, and error-handling implications have been considered

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• I would like to request that my diagnostic build log is removed before merging