Add admin ordering of items

[lkeegan]

• backend
  • add /*/order endpoints to re-order lists of
  • milestones
  • milestone-groups
  • child-questions
  • user-questions
• admin frontend
  • add "reorder" button to all lists of items that can be ordered
  • add OrderItemsModal dialog to re-order items using drag&drop
  • add svelte-dnd-action library for drag&drop functionality
• resolves #141

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 43.58974% with 44 lines in your changes missing coverage. Please review.

Project coverage is 30.39%. Comparing base (b75ded2) to head (a89c44b).

Files with missing lines	Patch %	Lines
...nd/src/lib/components/Admin/OrderItemsModal.svelte	0.00%	17 Missing and 1 partial :warning:
...nd/src/lib/components/Admin/MilestoneGroups.svelte	0.00%	14 Missing :warning:
frontend/src/lib/components/Admin/Questions.svelte	0.00%	9 Missing :warning:
...tend/src/lib/components/Admin/ReorderButton.svelte	0.00%	1 Missing and 1 partial :warning:
frontend/src/lib/components/Admin/AddButton.svelte	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #161 +/- ## ========================================== + Coverage 30.01% 30.39% +0.38% ========================================== Files 93 95 +2 Lines 3212 3287 +75 Branches 90 92 +2 ========================================== + Hits 964 999 +35 - Misses 2180 2218 +38 - Partials 68 70 +2 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.