[AndyScherzinger]

Part 4 of the conditional questions stack from #3123 (by Micke Nordin, with fixes by TimedIn and the review fixes). Based on #3835; the "Files changed" tab shows only this part.

Stack

1. Conditional questions: base with radio and dropdown questions #3833 Conditional questions: base with radio and dropdown questions
2. Conditional questions: branches on checkboxes #3834 Conditional questions: branches on checkboxes
3. Conditional questions: branches on date and time #3835 Conditional questions: branches on date and time
4. Conditional questions: branches on file upload #3836 Conditional questions: branches on file upload ← this PR
5. Conditional questions: branches on linear scale and color #3837 Conditional questions: branches on linear scale and color
6. Conditional questions: branches on short and long text #3838 Conditional questions: branches on short and long text

This PR

A file question shows a branch depending on whether a file was uploaded, so a branch can also stand for "no file uploaded".

• an unanswered file question opens its "no file uploaded" branch, other question types open nothing until answered;
• uploads are checked and stored like those of any file question (upload token of the same form);
• docs and tests.

Tests

• Unit tests: 641, all passing except the 15 IUserFolder errors main has as well.
• php-cs-fixer, psalm, eslint, vue-tsc (no new errors) and the build are clean.

🤖 AI (if applicable)

• The content of this PR was partly or fully generated using AI

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
lib/Service/SubmissionService.php	85.71%	1 Missing ⚠️

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