docs(jmap): JMAP usage documentation and autodoc stubs

[SashankBhamidi]

Summary

• Add docs/source/jmap.rst
• Add docs/source/caldav/jmap_client.rst
• Add docs/source/caldav/jmap_objects.rst
• Update docs/source/reference.rst
• Update docs/source/index.rst

Related #625

[Copilot]

Pull request overview

This PR adds comprehensive documentation for the JMAP calendar client support that was introduced in PR #625. The documentation provides user-facing guides and API reference stubs for Sphinx autodoc generation.

Changes:

• Added detailed JMAP usage guide covering authentication, calendar operations, event CRUD, search, sync, tasks, and error handling
• Added autodoc reference stubs for JMAP client and data object modules
• Updated the documentation index to include the new JMAP section

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
docs/source/jmap.rst	Comprehensive 377-line usage guide for JMAP client functionality including quick start, authentication methods, calendar operations, event CRUD, search, incremental sync, task support, async API, error handling, and configuration
docs/source/index.rst	Added jmap to the documentation table of contents after the async section
docs/source/reference.rst	Added references to caldav/jmap_client and caldav/jmap_objects autodoc stubs
docs/source/caldav/jmap_client.rst	Autodoc stub for JMAPClient and AsyncJMAPClient modules
docs/source/caldav/jmap_objects.rst	Autodoc stub for JMAP data objects (calendar, event, task) and error classes

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[SashankBhamidi]

Merging into feature/jmap.