feat: add reliability, dx, and tooling improvements

[brijr]

Summary

This PR adds comprehensive improvements across reliability, developer experience, tooling, and testing.

Reliability

• Structured error envelopes with consistent codes (META_AUTH_EXPIRED, META_RATE_LIMIT_USER, etc.) and human-readable messages
• Idempotency key system for write operations to prevent accidental duplicates
• Centralized Meta API error parsing with parseMetaApiError() and getHumanReadableError()
• Upload timeouts with AbortSignal support for uploadImageFromUrl()
• Enhanced retry with cancellation support via AbortSignal

Developer Experience

• Structured logging via META_MCP_LOG_LEVEL (debug/info/warn/error/silent) and META_MCP_LOG_FORMAT (json/text)
• CLI commands:
  • meta-ads-mcp config --client claude|cursor - Generate ready-to-use config JSON
  • meta-ads-mcp doctor - Validate environment, token scopes, and permissions

Tooling/UX

• get_account_context - Get accounts, currency, timezone, permissions in one call
• validate_campaign - Pre-creation validation for campaigns
• validate_ad_set - Pre-creation validation for ad sets
• validate_creative - Pre-creation validation for creatives
• summarize_errors - Convert Meta API errors to human-readable explanations with fix suggestions

Testing

• Jest configuration updated for TypeScript with ts-jest
• Mock fixtures using @faker-js/faker
• Contract tests for error-handler and rate-limiter

Files Changed

Category	Files
Types	src/types/error-envelope.ts
Utils	src/utils/logger.ts, src/utils/idempotency.ts, src/utils/error-handler.ts
CLI	src/cli/index.ts, src/cli/commands/config.ts, src/cli/commands/doctor.ts
Tools	src/tools/validation.ts
Core	src/server.ts, src/index.ts, src/meta-client.ts
Tests	__tests__/setup.ts, __tests__/fixtures/, __tests__/unit/
Config	package.json, jest.config.js

Test plan

• Run npm run build (may need NODE_OPTIONS="--max-old-space-size=8192" for large heap)
• Run npm test for unit tests
• Run npm run doctor to validate environment
• Run npm run config to generate Claude config
• Test new validation tools via MCP client