Document custom view settings

[simple-analytics-ai]

Depends on https://github.com/simpleanalytics/dashboard/pull/852. Merge and deploy dashboard #852 before merging this documentation PR.

Summary

Fixes #49

Implement the documentation update requested in dashboard #852. Add step 5 to the custom views guide covering how to open Settings, view-only scope, visibility permissions, number rounding and its plan requirement, and time zone. Update the page's modification date.

Security implications

• No security impact
• Has security impact - described as:

Testing

• Rendered the guide with Kramdown's GFM parser: five numbered steps, three nested settings bullets, and the edit URL placeholder escaped correctly; no parser warnings.
• Validated the YAML front matter and modification date.
• Checked settings labels, editing availability, visibility permissions, and the exact-numbers plan restriction against dashboard #852.
• Whitespace validation passed with git diff --check.

Checklist

• Linked to an issue
• Tested
• Asked for a review