chore: update analytics to May 2026

[MillenniumFalconMechanic]

Summary

Update static analytics site data to May 2026.

Steps

1. Update CURRENT_MONTH to "2026-05" in constants.py
2. Regenerate the static analytics site
3. Commit the updated data files

Additional changes

• Revert "Engaged Sessions" stat card back to "User Sessions" (total sessions). The engaged sessions metric was too restrictive, filtering out legitimate short visits. Bot noise is already handled by the suspicious page path filter.
• Fix HCA and LungMAP event_counts labels: "Cross-Dataset" → "Cross-Project" to match the entity type.
• Fix chart title bug: second chart in a pair was using the first chart's label instead of its own.
• Port click_url_regex support from data-portal branch into the shared analytics package: adds click URL filtering to _count_events, get_custom_event_change, and get_event_detail_table, and renders a "File" column in detail tables when click_url data is present.