Add search histograms and field summary charts

[jusso-dev]

Problem

The Hunt page lists matching records and field groups, but analysts need faster visual cues for time spikes, top entities, and unusual concentration before drilling into individual rows.

Scope

Add lightweight visual summaries to Hunt results: time histogram, top fields, and clickable pivots that narrow the active query.

Implementation Notes

• Build result aggregation helpers for count by time bucket, top hosts, top users, top processes, top IPs/domains, top rules, and severity distribution.
• Add a histogram above the Hunt result table.
• Make histogram buckets clickable to add a timestamp range clause.
• Make summary bars clickable to add an inclusive filter.
• Keep chart rendering compact and operational; avoid decorative dashboards.
• Reuse existing field group data where possible.

Acceptance Criteria

• Hunt results show a time histogram when records exist.
• Clicking a time bucket narrows the query to that bucket.
• Top field summaries show counts and add filters when clicked.
• Empty states remain clear when no results match.
• Charts do not cause layout shift on mobile or laptop widths.

Tests

• Unit test time bucket aggregation.
• Unit test filter query generation from chart clicks.
• Component test empty and populated histogram states.
• Regression test existing Hunt result table remains usable.