Add example of SQLite table relationships

[harshyadavDeveloper]

Description

Adds a small section demonstrating how to define relationships between tables in SQLite using foreign keys.

This enhances the existing tutorial by introducing a real-world use case without modifying the current flow of the guide.

Issues fixed by this PR

Closes #93073

PRs or commits this PR depends on

None

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[gemini-code-assist]

Code Review

This pull request adds a new section on using relationships between tables to the SQLite cookbook documentation. The review feedback suggests using the :::note container for consistency, adhering to the 80-character limit for semantic line breaks, and adding a note regarding the requirement to enable foreign key support in sqflite.

[sfshaza2]

/gcbrun

[sfshaza2]

lgtm. thx!

[flutter-website-bot]

Visit the preview URL for this PR (updated for commit 8040b0a):

https://flutter-docs-prod--pr13309-add-sqlite-relations-exampl-oiw98tci.web.app