Fix Docker Compose setup - command return types, composer install

[Gytkar]

What was changed

• Added missing return types to sample commands;
• Moved composer install to be run earlier;

Why?

• Fatal error in app container because of missing return types in sample commands - incompatible with Symfony\Component\Console\Command\Command::execute;
• Fatal error in app container because of missing vendors (composer install had to be run locally first, with all the pre-requisites, to get it to start up correctly);

Checklist

2. How was this tested: On multiple devices/OS'es, we could not successfully start the app container before solving both of these issues, or at least adding the return types and running composer install locally for the first time.

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