Add timezone-aware timestamp support and reporting improvements
Store timestamps in ISO-8601 format with timezone offsets
Accept client-local timestamps from browser and API
Normalize legacy naive timestamps during parsing
Add migration script for converting old SQLite timestamps
Fix mixed naive/aware datetime comparison errors
Render timestamps in browser-local timezone
Auto-generate default 7-day reports on page load
Expand default dashboard report to include all users
Preserve manual single-user report generation
Add curl-based validation/test script for API and report flows
