Overhaul fetch APIs

[mattt]

Follow up to #11

[Copilot]

Pull request overview

This PR introduces a typed, predicate-based fetch request API for querying Message and Chat records, as a follow-up to the model changes in #11.

Changes:

• Adds a generic FetchRequest<Result> API plus typed predicate/sort descriptor enums for messages and chats.
• Reworks Database fetching to support predicate compilation, sorting, and pagination via fetch(_:), while keeping deprecated legacy convenience wrappers.
• Expands test coverage for sorting/pagination, predicate composition, match modes, and pagination validation; updates README examples to the new API.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
Sources/iMessage/FetchRequest.swift	Adds the new public typed fetch request, predicates, sort descriptors, and defaults for Message/Chat.
Sources/iMessage/Database.swift	Implements fetch(_:) for typed requests, predicate compilation to SQL, ORDER BY generation, and pagination validation; keeps deprecated wrappers.
Tests/iMessageTests/DatabaseTests.swift	Adds tests covering pagination/sort, predicate composition, match modes, empty-compound semantics, legacy wrapper parity, and invalid pagination.
README.md	Updates dependency version and replaces legacy fetch example with the predicate-style FetchRequest usage.

---

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