Improve Time Tracking Overview

[knollengewaechs]

Detailed Description

• [omittted] Find better chart for time-line view
• Improve table in time tracking overview, see https://scm.slack.com/archives/C5AKLAV0B/p1708951683131989?thread_ts=1704359796.147499&cid=C5AKLAV0B
• remove detail view and integrate data to overview

Discuss requirements:

• [x] what is in the csv in detail? (user name/id/email? dataset orga/name or id?)
• [x] csv export of whole table: include per-annotation lines? or just sums of users?
• [x] How should this look for a non-privileged user (see only themselves in list I guess?)

TOOD back-end:

• [x] api/time/user/:userId/summedByAnnotation return summed per annotation for expanded table
• [x] api/time/overview return number of tasks and average time per task?
• [x] api/time/user/:userId/spans route for csv download per user
• [x] adapt e2e tests

ToDos frontend:

• [x] add export button to export user time spans
• [x] add stats:
  • [x] no tasks,
  • [x] avg time per task per user;
  • [x] segments and trees per task/annotation
• [x] show id of annotation/task
• [x] group time spans per annotation/task
• [x] fix sorting in table
• [x] fix details: data is not matching overview

Follow-up for #5375