fix: address 4 issues - wallet validation, route error boundaries, DataRefreshWrapper timers, wallet emoji icons

[Penielka]

Summary

Fixes 4 issues assigned to @Penielka:

#429 (P1, security): wallet address not checksum-validated before provider calls

• Created src/utils/walletHelpers.ts with assertValidAddress using viem's getAddress for EIP-55 checksum validation
• Added fetchWalletBalance that validates address before any provider call
• Throws user-safe error messages on invalid or malformed addresses
• Added comprehensive unit tests with well-known checksums and adversarial examples

#428 (P2, refactor): missing route-level error boundaries in app routes

• Wrapped 7 pages with withRouteErrorBoundary: compare, governance, secondary-market, tax-report, mobile-properties, widget/investment-calculator, developers/tokenize
• Errors caught at route level now report to /api/errors monitoring endpoint
• Uncaught errors continue to bubble to app/error.tsx with breadcrumb context

#435 (P2, ux): DataRefreshWrapper drops form state and stacks timers

• Added useRef to track pending success timeout, with cleanup on unmount via useEffect
• Cancels pending timers when a new refresh is triggered, preventing timer stacking
• Children no longer remount across refreshes (form state preserved)
• Added tests verifying timer cleanup and form state preservation

#434 (P3, ux): emoji wallet icons render unreliably on some platforms

• Replaced raw emoji with lucide-react SVG icons: Wallet (MetaMask), QrCode (Coinbase), Link2 (WalletConnect)
• Added title and aria-label attributes for accessibility
• Fixed corrupted duplicate wallet arrays in the file

Closes #428, Closes #429, Closes #434, Closes #435

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