feat: add maximum submissions limit for forms

[LAfricain]

Add the ability to limit the number of responses a form can receive. When the limit is reached, the form is automatically closed and displays a dedicated message instead of accepting new submissions.

• Add max_submissions column to forms_v2_forms table (migration)
• Add maxSubmissions property to Form entity
• Check submission limit in FormsService::canSubmit()
• Add limit enforcement in ApiController::newSubmission()
• Add isMaxSubmissionsReached flag in form API response
• Add limit settings UI in SettingsSidebarTab
• Display dedicated 'Form is full' message in Submit view
• Add French translations for new strings

Closes #596

[Chartman123]

@LAfricain thanks for your PR. I just had a quick look at your code and didn't test it yet in my instance. Already a few comments. :)

[Chartman123]

Some more comments :) Please have a look at the failing workflows, too.

[LAfricain]

Hello @Chartman123,
I would like to know if everything is ready for a merge or if there are still some improvements to be made?
Thank you in any case for this tool!

[Chartman123]

@LAfricain sorry, I don't have much spare time at the moment :) Please fix the remaining workflow issues

[LAfricain]

I don't have much spare time at the moment :)

It's Ok, no rush. I didn't realize I had to fix the errors myself; I still need to get used to the tool. It's done now.

[Chartman123]

@LAfricain yes, you have to fix them yourself (or use the npm scripts and php scripts). Environments like VSCode also can assist you with that :)