add stellar error decoder

[ZuLu0890]

Summary

Closes #10.

Adds a reusable Stellar/Soroban error decoding layer so raw transaction and contract failures can be translated into user-facing messages with troubleshooting guidance.

What changed

• Added src/data/errorCodes.json with typed mappings for common Stellar transaction, operation, and Soroban failure modes.
• Added resolveError in src/utils/errorDecoder.ts to normalize Horizon/Soroban error shapes, infer contract failures, format ICU-style placeholders, and fall back to a generic decoded error.
• Added starter consumer hooks for billing and ledger event flows.
• Added a shared ErrorToast component with severity styling, troubleshooting expansion, and docs links.
• Added a telemetry helper plus a Next route to capture unknown Stellar error codes for future dictionary expansion.

Impact

Users should see actionable explanations like missing signatures, underfunded operations, expired transactions, storage failures, and access violations instead of opaque SDK strings such as tx_failed, op_underfunded, or generic host exceptions.

Validation

• Confirmed src/data/errorCodes.json parses successfully with PowerShell ConvertFrom-Json.
• Ran git diff --check and git diff --cached --check successfully.
• Could not run npm run build or npm run lint locally because this shell does not have Node/npm on PATH.
  closes Human-Readable Dictionary Mapping Cryptic Stellar Node Exceptions #10

[JamesEjembi]

fix errors and ensure all tests are passsed