Feature Request: Session-level view in web UI

[github-actions[bot]]

Originally posted as issue #336 by @changluyi
#336

Feature Request

Currently the web UI shows observations as a continuous stream. It would be helpful to have a session-level view where users can:

1. Browse sessions in a list (with timestamp, observation count, summary)
2. Click into a session to see all observations within that session
3. Navigate between sessions easily

Use case:
When I want to review what was done in a previous work session, I need to browse by session rather than scrolling through the observation stream.

Example:

Sessions
├─ 2024-12-16 09:30 - Session1 (45 observations)
├─ 2024-12-15 14:20 - Session2 (32 observations)  
└─ 2024-12-15 10:00 - Session3 (18 observations)

Click any session to see its summary.