feat: board and card import from CSV / JSON

[miaulalala]

• Target version: main

Summary

Allows importing a new board from CSV /JSON and adding / updating cards for existing boards from CSV / JSON.

Import board:

Import cards:

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Documentation (manuals or wiki) has been updated or is not required
• This PR was partly or wholly created by AI

[github-actions]

🐢 Performance warning.
It looks like the query count of the integration tests increased with this PR.
Database query count is now 101647 was 93102 (+9.17%)
Please check your code again. If you added a new test this can be expected and the base value in tests/integration/base-query-count.txt can be increased.

[github-actions]

🐢 Performance warning.
It looks like the query count of the integration tests increased with this PR.
Database query count is now 101639 was 93102 (+9.16%)
Please check your code again. If you added a new test this can be expected and the base value in tests/integration/base-query-count.txt can be increased.

[github-actions]

🐢 Performance warning.
It looks like the query count of the integration tests increased with this PR.
Database query count is now 101638 was 93102 (+9.16%)
Please check your code again. If you added a new test this can be expected and the base value in tests/integration/base-query-count.txt can be increased.

[github-actions]

🐢 Performance warning.
It looks like the query count of the integration tests increased with this PR.
Database query count is now 101650 was 93102 (+9.18%)
Please check your code again. If you added a new test this can be expected and the base value in tests/integration/base-query-count.txt can be increased.

[github-actions]

🐢 Performance warning.
It looks like the query count of the integration tests increased with this PR.
Database query count is now 101637 was 93102 (+9.16%)
Please check your code again. If you added a new test this can be expected and the base value in tests/integration/base-query-count.txt can be increased.

[github-actions]

🐢 Performance warning.
It looks like the query count of the integration tests increased with this PR.
Database query count is now 101649 was 93102 (+9.18%)
Please check your code again. If you added a new test this can be expected and the base value in tests/integration/base-query-count.txt can be increased.

[github-actions]

🐢 Performance warning.
It looks like the query count of the integration tests increased with this PR.
Database query count is now 101662 was 93102 (+9.19%)
Please check your code again. If you added a new test this can be expected and the base value in tests/integration/base-query-count.txt can be increased.

[github-actions]

🐢 Performance warning.
It looks like the query count of the integration tests increased with this PR.
Database query count is now 101649 was 93102 (+9.18%)
Please check your code again. If you added a new test this can be expected and the base value in tests/integration/base-query-count.txt can be increased.

[github-actions]

🐢 Performance warning.
It looks like the query count of the integration tests increased with this PR.
Database query count is now 101644 was 93102 (+9.17%)
Please check your code again. If you added a new test this can be expected and the base value in tests/integration/base-query-count.txt can be increased.

[github-actions]

🐢 Performance warning.
It looks like the query count of the integration tests increased with this PR.
Database query count is now 101645 was 93102 (+9.17%)
Please check your code again. If you added a new test this can be expected and the base value in tests/integration/base-query-count.txt can be increased.