feat(errors): implement human-readable Stellar and Soroban error decoder (#180)

[Simultech369]

Summary of Changes

This pull request resolves #180 by implementing a human-readable dictionary and decoding pipeline mapping cryptic Stellar Horizon transaction errors (tx_failed, op_underfunded, tx_bad_seq, op_no_trust) and Soroban RPC HostError / ContractError codes into actionable diagnostics with recommended troubleshooting steps.

🎯 Key Implementations

1. src/utils/errorDecoder.ts — Error Catalog & High-Performance Decoder

   • ERROR_CATALOG: Strongly-typed dictionary mapping 60+ low-level transaction codes, operation codes, Soroban host errors, contract revert codes, and wallet/network errors into human descriptions and troubleshooting steps.
   • extractErrorMessage: Normalizes arbitrary error inputs (strings, Error instances, Axios/Fetch errors, JSON-RPC responses, Horizon result_codes).
   • decodeTransactionError: High-performance regex and code matching executing in under 0.01ms per lookup (< 0.1ms target).
   • Dynamic Interpolation: Automatically extracts and interpolates parameters (e.g. ContractError(#)).
   • Graceful Fallbacks: Comprehensive handling of edge cases (null, undefined, empty string, numbers, unknown errors).

2. src/components/shared/ErrorDisplay.tsx — Accessible Error Display Component

   • Severity badges (Critical Error, Warning, Notice) with distinct theme styling.
   • Numbered step-by-step troubleshooting checklist.
   • External documentation links (docsUrl) when available.
   • "Copy Error Details" button with instant clipboard confirmation.
   • Expandable technical details accordion displaying raw codes and timestamps.
   • Optional onDismiss and onRetry callbacks.

3. API Integration (src/lib/api/staking.ts)

   • Wrapped transaction submission failures with decodeTransactionError.

4. Comprehensive Unit & Component Tests (src/__tests__/errorDecoder.test.ts, src/__tests__/ErrorDisplay.test.tsx)

   • 29/29 dedicated tests verifying catalog coverage, error categorization, regex extractions, edge cases, performance benchmarks, and React component interactivity.

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🧪 Verification & Testing

• npm run test:unit: