E2E: Events investigation feed and filters

[Bccorb]

Part of #176. Depends on #177.

Goal

Cover the Events investigation feed: browsing authentication events, filtering by grouped category and time range, and the URL-driven filter state that makes views deep-linkable.

Scope

• Feed renders seeded events grouped and categorized correctly.
• Category filter narrows the feed to the selected grouped event types.
• Time-range filter narrows the feed to the selected window.
• Filter state is reflected in the URL, and loading a deep link reproduces the filtered view.
• Clearing or changing filters updates both the feed and the URL.
• Navigating into an individual event lands on the correct target (for example a user or session).
• Loading, empty (no events match), and error states render correctly.

Key files

src/pages/Events.tsx, src/components/EventFilters.tsx, src/hooks/useEvents.ts, src/hooks/useGroupedEvents.ts, src/lib/eventCategories.ts, src/lib/eventGroups.ts, src/lib/eventMapping.ts, src/lib/eventNavigation.ts, src/lib/timeRange.ts.