IOS-5454 Fix chat sorting by adding auto-enrichment for date sorts

[ignatovv]

Summary

• Add auto-enrichment for date sorts in SearchHelper - automatically sets format = .date and includeTime = true for date-type relations
• Expand dateKeys list to include all date-type bundled properties (lastMessageDate, dueDate, addedDate, etc.)
• Remove now-redundant includeTime parameter from SearchHelper.sort() method
• Reorganize SearchHelper with MARK comments for better code organization

Note: Cross-space search (used by ChatDetailsSubscriptionBuilder) doesn't support sorting on the middleware side yet, so chat list sorting will be addressed separately when middleware adds support.

[claude]

✅ Approved - No issues found