feat(api): stabilize API and client contracts

[ShashankShekhar31]

API & Client Contract Stabilization

Summary

• Added versioned API contract definitions for the v1 REST API.
• Added generated OpenAPI TypeScript definitions and OpenAPI JSON output.
• Standardized shared HTTP success/error response types.
• Centralized API error handling across the Fastify server.
• Stabilized authentication, health, logout, and refresh route response contracts.
• Added explicit request/response schemas and API documentation metadata.
• Preserved request correlation IDs through API responses.
• Added and expanded error-handler test coverage.
• Maintained API rate limiting and security controls.
• Updated API package dependencies and lockfile as required.

Validation

• pnpm audit --audit-level high — passed
• pnpm run format:check — passed
• pnpm lint — passed
• pnpm typecheck — passed
• pnpm --filter @crypto-wallet/storage migrate-all — passed
• pnpm test — passed
• pnpm build — passed
• git diff --check — passed

Scope

This PR completes API & Client Contract Stabilization