feat(frontend): Implement client-side SSE handling (#35)

Implements real-time event streaming on the frontend with:

- Event types and type guards matching backend EventType enum
- Zustand-based event store with per-project buffering
- useProjectEvents hook with auto-reconnection and exponential backoff
- ConnectionStatus component showing connection state
- EventList component with expandable payloads and filtering

All 105 tests passing. Follows design system guidelines.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/components/events/index.ts

@@ -0,0 +1,10 @@
+/**
+ * Event Components
+ *
+ * Components for displaying real-time project events via SSE.
+ *
+ * @module components/events
+ */
+
+export { ConnectionStatus } from './ConnectionStatus';
+export { EventList } from './EventList';