docs: add batch jobs quickstart guide

[jlugao]

Summary

• Added comprehensive documentation for the batch jobs feature (import_jobs() method)
• New file: docs/batch_jobs.md with complete quickstart guide
• Updated mkdocs.yml to include the new documentation page

Changes

• New documentation file: Created docs/batch_jobs.md covering:
  • Quick example with step-by-step instructions for importing batch jobs
  • Advanced usage with jobs_list for explicit control over job metadata
  • Explanation of automatic discovery vs explicit definition approaches
  • Job types (condition, action, job) and their differences
  • Best practices for organizing batch jobs by domain
  • Complete working examples with order processing use case
• Updated navigation: Added "Batch Jobs" entry to Tutorial section in mkdocs.yml

Related Issue

Closes #50

Testing

• Documentation builds successfully: poetry run poe docs-build
• All quality checks pass: poetry run poe check-all (lint, format, typecheck, test)